Hybrid drive device

ABSTRACT

A hybrid drive device has a clutch connecting and disconnecting an output shaft and an input shaft, a first motor generator that rotates in conjunction with the rotation of the input shaft, an allowable clutch heat generation amount calculation portion that calculates the allowable clutch heat generation amount, an allowable differential clutch rotation speed calculation portion which calculates the allowable differential clutch rotation speed for when engagement starts, on the basis of the allowable clutch heat generation amount, and a motor generator rotation control portion that controls the rotation speed of the first motor generator such that the differential clutch rotation speed when engagement starts and during engagement is no more than the allowable differential clutch rotation speed when engagement starts.

TECHNICAL FIELD

This invention relates to a hybrid drive device which is equipped with aclutch for connecting or disconnecting the output shaft of the engineand the input shaft of a gear mechanism and a motor/generator rotatingin association with the rotation of the input shaft.

BACKGROUND ART

Conventionally, a hybrid drive device has been proposed as shown in thePatent Literature 1, which is formed by an engine, a clutch connectingor disconnecting the output shaft of the engine and an input shaft ofthe gear mechanism and a motor/generator rotating in association withthe rotation of the input shaft. According to this hybrid drive deviceshown in the Patent Literature 1, the engine is restarted from theengine being in a stopped state by gradually increasing the enginerotation speed by gradually transmitting the rotation drive force fromthe motor/generator to the engine by gradually connecting the clutchwhich has been in a disconnected state.

CITATION LIST Patent Literature

Patent Literature 1: JP2010-76678 A

SUMMARY OF INVENTION Technical Problem(s)

However, according to the hybrid drive device disclosed in the abovePatent literature 1, the engine is re-started by gradually engaging theclutch which has been in the disconnected state and accordingly, whenthe engine re-starting is very frequently performed, or when the engineis in a low temperature environment state and friction torque of theengine is relatively large, a heat generated due to the clutch slidingoperation becomes very high which may lead to a shortening of lifeduration of the clutch or generation of a deterioration of performanceproperty of the clutch, which would be a problem of such conventionalclutch.

The present invention was made in consideration with the above problemsand the object of the invention is to provide a technology that canprevent overheating of a clutch in a hybrid drive device having theclutch for connecting or disconnecting the output shaft of the engineand the input shaft of a gear mechanism and a motor/generator rotatingin association with the rotation of the input shaft.

Solution to Problem(s)

The invention associated with claim 1 to solve the above problems ischaracterized in that the hybrid drive device includes an engine whichoutputs a rotation drive force to an output shaft, an input shaft whichis rotated in association with a rotation of a drive wheel, a clutchdisposed between the output shaft and the input shaft for connecting ordisconnecting the output shaft and the input shaft, a motor/generatorwhich is rotated in association with a rotation of the input shaft, anallowable clutch heat generation amount calculating means forcalculating an allowable clutch heat generation amount which correspondsto a heat generation amount that the clutch can allow under the clutchbeing in engagement and a motor/generator rotation control means forcontrolling a rotation speed of the motor/generator not to exceed theallowable clutch heat generation amount calculated by the allowableclutch heat generation amount calculating means.

According to the invention associated with claim 2, in addition to thefeature of claim 1, the hybrid drive device further includes anallowable clutch difference rotation speed calculating means forcalculating an allowable clutch difference rotation speed whichcorresponds to a difference rotation speed between the output shaft andthe input shaft based on the allowable clutch heat generation amount,wherein the motor/generator rotation control means controls the rotationspeed of the motor/generator so that a clutch difference rotation speedwhich corresponds to the difference rotation speed between the outputshaft and the input shaft becomes equal to or less than the allowableclutch difference rotation speed. It is preferable for themotor/generator rotation control means to control the rotation speed ofthe motor/generator so that the clutch difference rotation speed underthe clutch being in engagement is gradually decreased with time from astart of engagement of the clutch.

According to the invention associated with claim 3, in addition to thefeature of claim 1 or 2, the hybrid drive device further includes aclutch temperature obtaining means for obtaining a current clutchtemperature wherein the allowable clutch heat generation amountcalculating means calculates the allowable clutch heat generation amountbased on the current clutch temperature and a clutch allowabletemperature which corresponds to a temperature that is an allowabletemperature for the clutch.

According to the invention associated with claim 4, in addition to thefeature of claim 2 or 3, the allowable clutch difference rotation speedcalculating means calculates the allowable clutch difference rotationspeed at a start of engagement which corresponds to the differencerotation speed between the output shaft and the input shaft at the startof engagement of the clutch and the motor/generator rotation controlmeans controls the rotation speed of the motor/generator so that theclutch difference rotation speed at the start of engagement whichcorresponds to the difference rotation speed between the output shaftand the input shaft at the start of engagement of the clutch becomesequal to or less than the allowable clutch difference rotation speed atthe start of engagement.

According to the invention associated with claim 5, in addition to thefeature of claim 2 or 3, the allowable clutch difference rotation speedcalculating means calculates the allowable clutch difference rotationspeed at the start of engagement which corresponds to the differencerotation speed between the output shaft and the input shaft at the startof engagement of the clutch and engages the clutch under a currentclutch difference rotation speed, when the clutch difference rotationspeed before the start of engagement of the clutch is equal to or lessthan the allowable clutch difference rotation speed at the start ofengagement.

According to the invention associated with claim 6, in addition to thefeature of claim 4 or 5, the allowable clutch difference rotation speedcalculating means calculates the allowable clutch difference rotationspeed at the start of engagement based on the allowable clutch heatgeneration amount, a friction torque of the engine, an inertia of theengine and a target clutch synchronizing time which is a target elapsedtime from the start of engagement of the clutch to a completion ofsynchronization of the output shaft and the input shaft.

According to the invention associated with claim 7, in addition to thefeature of any one of claims 4 through 6, the hybrid drive devicefurther includes a target input shaft rotation speed calculating meanswhich calculates a target input shaft rotation speed which correspondsto a target rotation speed of the input shaft under the clutch being inengagement based on the allowable clutch difference rotation speed atthe start of engagement and the target clutch synchronizing time whichis the target elapsed time from the start of engagement of the clutch tothe completion of synchronization of the output shaft and the inputshaft, wherein the motor/generator rotation control means controls therotation speed of the motor/generator so that the rotation speed of theinput shaft under the clutch being in engagement becomes equal to orless than the target input shaft rotation speed. It is preferable thatthe target input shaft rotation speed calculating means calculates thetarget clutch difference rotation speed also considering an enginerotation speed which corresponds to the rotation speed of the outputshaft.

According to the invention associated with claim 8, in addition to thefeature of claim 7, the target input shaft rotation speed calculatingmeans calculates the target input shaft rotation speed so that thetarget input shaft rotation speed becomes zero upon an elapse of thetarget clutch synchronizing time from the start of engagement of theclutch by gradually decreasing with time and the motor/generatorrotation control means controls the rotation speed of themotor/generator so that the rotation speed of the input shaft under theclutch being in engagement becomes the target input shaft rotationspeed.

According to the invention associated with claim 9, in addition to thefeature of any one of claims 4 through 6, the hybrid drive devicefurther includes a target clutch difference rotation speed calculatingmeans which calculates a target clutch difference rotation speed whichcorresponds to a target clutch difference rotation speed under theclutch being in engagement based on the clutch allowable differencerotation speed at the start of engagement and the target clutchsynchronizing time which corresponds to the target elapsed time from thestart of engagement of the clutch to the completion of synchronizationof the output shaft and the input shaft, wherein the motor/generatorrotation control means controls the rotation speed of themotor/generator so that the clutch difference rotation speed under theclutch being in engagement becomes equal to or less than the targetclutch difference rotation speed. It is noted that it is preferable thatthe target clutch difference rotation speed calculating means calculatesthe target clutch difference rotation speed also considering the enginerotation speed which corresponds to the rotation speed of the outputshaft.

According to the invention associated with claim 10, in addition to thefeature of claim 9, the target clutch difference rotation speedcalculating means calculates the clutch difference rotation speed sothat the clutch difference rotation speed becomes zero upon an elapse ofthe target clutch synchronizing time from the start of engagement of theclutch by gradually decreasing with time and the motor/generatorrotation control means controls the rotation speed of themotor/generator so that the clutch difference rotation speed under theclutch being in engagement becomes the target clutch difference rotationspeed.

According to the invention associated with claim 11, in addition to thefeature of any one of claims 4 through 10, a relationship between theallowable clutch difference rotation speed and the elapsed time from thestart of engagement of the clutch indicates a direct function in whichthe allowable clutch difference rotation speed gradually decreases asthe elapsed time increases.

According to the invention associated with claim 12, in addition to thefeature of any one of claims 1 through 3, the hybrid drive devicefurther includes an allowable clutch synchronizing time calculatingmeans which calculates an allowable clutch synchronizing time whichcorresponds to the allowable clutch synchronizing time when the clutchis engaged based on the allowable clutch heat generation amount and themotor/generator rotation control means controls the rotation speed ofthe motor/generator so that the clutch difference rotation speed becomeszero in a time equal to or less than the allowable clutch synchronizingtime by gradually decreasing with time from the start of engagement ofthe clutch.

According to the invention associated with claim 13, in addition to thefeature of any one of claims 1 through 12, the hybrid drive devicefurther includes a target clutch transmitting torque calculating meansfor calculating a target clutch transmitting torque which corresponds toa transmitting torque under the clutch being in engagement and a clutchcontrol means for controlling the clutch so that the transmitting torqueunder the clutch being in engagement becomes the target clutchtransmitting torque.

Advantageous effects of Invention

According to the invention associated with claim 1, the allowable clutchheat generation amount calculating means calculates the allowable clutchheat generation amount which corresponds to the heat generation amountthat the clutch can allow and the motor/generator rotation control meanscontrols the rotation speed of the motor/generator not to exceed theallowable clutch heat generation amount. Accordingly, the clutch heatgeneration amount can be limited to the allowable heat generation amountor less. This can avoid an overheating of the clutch.

According to the invention of claim 2, the allowable clutch differencerotation speed calculating means calculates the allowable clutchdifference rotation speed which corresponds to the difference inrotation speed between the output shaft and the input shaft based on theallowable clutch heat generation amount and the motor/generator rotationcontrol means controls rotation speed of the motor/generator so that theclutch difference rotation speed which is the difference in rotationspeed between the output shaft and the input shaft becomes equal to orless than the allowable clutch difference rotation speed. Accordingly, achange of the clutch difference rotation speed due to a vehicle speedchange or an increase ratio of the engine rotation speed can beminimized. Since the clutch difference rotation speed is controlled notto exceed the allowable heat generation amount, the heat generation ofthe clutch can be assuredly limited to equal to or less than theallowable heat generation amount.

According to the invention of claim 3, the allowable clutch heatgeneration amount calculating means calculates the allowable clutch heatgeneration amount based on the current clutch temperature and a clutchallowable temperature which corresponds to a temperature that can beallowed for the clutch. Since the clutch temperature is dropped to theallowable temperature or less when the clutch is engaged, even thecurrent temperature of the clutch indicates any temperature the clutchoverheating can be surely prevented.

According to the invention associated with claim 4, the allowable clutchdifference rotation speed calculating means calculates the allowableclutch difference rotation speed at the start of engagement and themotor/generator rotation control means controls the rotation speed ofthe motor/generator so that the clutch difference rotation speed at thestart of engagement becomes equal to or less than the allowable clutchdifference rotation speed at the start of engagement. Accordingly, theclutch difference rotation speed is set to be equal to or less than theallowable clutch difference rotation speed at the start of engagementwhich is calculated not to exceed the allowable clutch heat generationamount before the clutch engagement, the clutch heat generation amountunder the clutch being in engagement would not exceed the allowableclutch heat generation amount and a heat generation amount excessivelyover the allowable clutch heat generation amount can be surelyprevented.

According to the invention associated with claim 5, the allowable clutchdifference rotation speed calculating means calculates the allowableclutch difference rotation speed at the start of engagement whichcorresponds to the difference rotation speed between the output shaftand the input shaft at the start of engagement of the clutch and engagesthe clutch under a current clutch difference rotation speed, when theclutch difference rotation speed before the start of engagement of theclutch is equal to or less than the allowable clutch difference rotationspeed at the start of engagement. Therefore, it is confirmed that theheat generation amount under the clutch being in engagement would notexceed the allowable clutch heat generation amount and after theconfirmation, the clutch is engaged under the current clutch differencerotation speed without controlling of the clutch difference rotationspeed by the motor/generator at the start of engagement of the clutch.Thus a prompt clutch engagement operation can be performed to saveenergy consumption by eliminating controlling of the clutch differencerotation speed by the motor/generator.

According to the invention associated with claim 6, the allowable clutchdifference rotation speed calculating means calculates the allowableclutch difference rotation speed at the start of engagement based on theallowable clutch heat generation amount, a friction torque of theengine, inertia of the engine and a target clutch synchronizing time.Accordingly, since the allowable clutch difference rotation speed at thestart of engagement can be calculated considering the friction torque ofthe engine, the inertia of the engine and the target clutchsynchronizing time, the clutch heat generation amount can be surelylimited to the allowable clutch heat generation amount, regardless ofthe friction torque of the engine, the inertia of the engine and thetarget clutch synchronizing time. This can surely prevent an overheatingof the clutch and accordingly, any clutch engagement interruption can beavoided, which may occur due to an overheating of the clutch and aprompt and sure clutch engagement operation can be performed.

According to the invention associated with claim 7, the target inputshaft rotation speed calculating means calculates the target input shaftrotation speed based on the allowable clutch difference rotation speedat the start of engagement and the target clutch synchronizing time.Further, the motor/generator rotation control means controls therotation speed of the motor/generator so that the rotation speed of theinput shaft under the clutch being in engagement becomes equal to orless than the target input shaft rotation speed. Accordingly, the clutchsynchronization can be surely performed within the target clutchsynchronizing time by calculating the target input shaft rotation speedwhich can synchronize the clutch after the target clutch synchronizingtime lapsed from the start of engagement of the clutch. Thus the heatgeneration of the clutch during engagement can be limited to theallowable clutch heat generation amount to prevent overheating of theclutch.

According to the invention associated with claim 8, the target inputshaft rotation speed calculating means calculates the target input shaftrotation speed so that the target input shaft rotation speed becomeszero upon an elapse of the target clutch synchronizing time from thestart of engagement of the clutch by gradually decreasing with time. Themotor/generator rotation control means controls the rotation speed ofthe motor/generator so that the rotation speed of the input shaft underthe clutch being in engagement becomes the target input shaft rotationspeed. Therefore, the clutch difference rotation speed is controlled tobe decreased gradually with time from the start of engagement of theclutch, the heat generation amount at the time of clutch engagement canbe suppressed to the allowable clutch heat generation amount and at thesame time generation of the shocks of the vehicle can be prevented.

According to the invention associated with claim 9, the target clutchdifference rotation speed calculating means calculates a target clutchdifference rotation speed based on the clutch allowable differencerotation speed at the start of engagement and the target clutchsynchronizing time and the motor/generator rotation control meanscontrols the rotation speed of the motor/generator so that the clutchdifference rotation speed under the clutch being in engagement becomesequal to or less than the target clutch difference rotation speed.Accordingly, the clutch synchronization can be surely performed withinthe target clutch synchronizing time by calculating the target clutchdifference rotation speed which satisfies the allowable clutchdifference rotation until the clutch is synchronized after the targetclutch synchronizing time lapsed from the start of engagement of theclutch. Thus the heat generation of the clutch during engagement can belimited to the allowable clutch heat generation amount to preventoverheating of the clutch.

According to the invention associated with claim 10, the target clutchdifference rotation speed calculating means calculates the clutchdifference rotation speed so that the clutch difference rotation speedbecomes zero upon an elapse of the target clutch synchronizing time fromthe start of engagement of the clutch by gradually decreasing with time.Further, the motor/generator rotation control means controls therotation speed of the motor/generator so that the clutch differencerotation speed under the clutch being in engagement becomes the targetclutch difference rotation speed. Accordingly, since the clutchdifference rotation speed is controlled to be gradually decreased withtime from the start of engagement of the clutch, the heat generationamount at the time of engagement of the clutch can be limited to equalto or less than the allowable heat generation amount and generation ofthe vehicle shocks can be prevented.

According to the invention associated with claim 11, the relationshipbetween the allowable clutch difference rotation speed and the elapsedtime from the start of engagement of the clutch indicates a directfunction in which the allowable clutch difference rotation speedgradually decreases as the elapsed time increases. Accordingly, based onthe allowable clutch heat generation amount, the clutch differencerotation speed at the start of engagement can be surely and easilycalculated.

According to the invention associated with claim 12, the hybrid drivedevice further includes an allowable clutch synchronizing timecalculating means which calculates an allowable clutch synchronizingtime which corresponds to the allowable clutch synchronizing time whenthe clutch is engaged based on the allowable clutch heat generationamount and the motor/generator rotation control means controls therotation speed of the motor/generator so that the clutch differencerotation speed becomes zero in a time period of the allowable clutchsynchronizing time or less by gradually decreasing with time from thestart of engagement of the clutch. Accordingly, since the clutchsynchronizing time before the clutch being engaged is set to be lessthan the allowable clutch synchronizing time which is calculated not toexceed the allowable clutch heat generation amount, the heat generationamount under the clutch being in engagement can be prevented fromexceeding the allowable clutch heat generation amount.

According to the invention associated with claim 13, the hybrid drivedevice further includes a target clutch transmitting torque calculatingmeans for calculating a target clutch transmitting torque whichcorresponds to a transmitting torque under the clutch being inengagement and a clutch control means for controlling the clutch so thatthe transmitting torque under the clutch being in engagement becomes thetarget clutch transmitting torque. Accordingly, the clutch transmittingtorque would not be changed and be kept to be constant at the time ofclutch engagement. Thus, since the clutch transmitting torque becomesconstant at the time of engagement of the clutch 20, the clutch heatgeneration amount which depends on the transmitting torque can belimited to the allowable clutch heat generation amount which isestimated in advance.

BRIEF EXPLANATION OF ATTACHED DRAWINGS

FIG. 1 is a skeleton view indicating the structure of a hybrid drivedevice according to a first embodiment of the invention;

FIG. 2A is a velocity diagram of the planetary gear mechanism underelectrically operated running mode and under hybrid running mode;

FIG. 2B is a velocity diagram of the planetary gear mechanism underelectrically operated running mode and under hybrid running mode;

FIG. 3 is a flowchart of a program executed at the control portionillustrated in FIG. 1 for clutch engine control;

FIG. 4 is a flowchart of a program executed at the control portionillustrated in FIG. 1 for engine start control according to the firstembodiment;

FIG. 5 is a flowchart of allowable clutch difference rotation speed atthe start of engagement which is a sub-routine of the control programexecuted at the control portion shown in FIG. 1;

FIG. 6 is a graph, the vertical axis thereof indicating a clutch heatgeneration amount Q and the horizontal axis indicating a clutchdifference rotation speed Δ{tilde over (ω)} _(—)0 at the start ofengagement of the clutch and the graph shows the relationship betweenthe allowable clutch heat generation amount Qtmax, actual clutch heatgeneration amount Qr and the clutch difference rotation speed Δ{tildeover (ω)} _(—)0 at the start of engagement of the clutch;

FIG. 7A is a graph, the horizontal axis thereof indicating the elapsedtime “t” from the start of engagement of the clutch and the verticalaxis thereof indicating the clutch difference rotation speed Δ{tildeover (ω)}, wherein the graph shows the relationship between theallowable clutch difference rotation speed Δ{tilde over (ω)} max and theelapsed time “t” from the start of engagement of the clutch when theinput shaft rotation speed at the start of engagement is equal to orless than the allowable clutch difference rotation speed at the start ofengagement;

FIG. 7B is a graph, the horizontal axis thereof indicating the elapsedtime “t” from the start of engagement of the clutch and the verticalaxis thereof indicating the clutch difference rotation speed Δ{tildeover (ω)}, wherein the graph shows the relationship between theallowable clutch difference rotation speed Δ{tilde over (ω)} max and theelapsed time “t” from the start of engagement of the clutch when theinput shaft rotation speed at the start of engagement is larger than theallowable clutch difference rotation speed at the start of engagement;

FIG. 8 is a flowchart of a control program executed at the controlportion illustrated in FIG. 1 for a first engine start processing;

FIG. 9 is a flowchart of a control program executed at the controlportion illustrated in FIG. 1 for a second engine start processing;

FIG. 10A is a graph, the horizontal axis thereof indicating the elapsedtime “t” from the start of engagement of the clutch and the verticalaxis thereof indicating the clutch difference rotation speed Δ{tildeover (ω)}, wherein the graph shows the relationship between theallowable clutch difference rotation speed Δ{tilde over (ω)} max and theelapsed time “t” from the start of engagement of the clutch when thedefined clutch synchronizing time is equal to or less than the allowableclutch synchronizing time;

FIG. 10B is a graph, the horizontal axis thereof indicating the elapsedtime “t” from the start of engagement of the clutch and the verticalaxis thereof indicating the clutch difference rotation speed Δ{tildeover (ω)}, wherein the graph shows the relationship between theallowable clutch difference rotation speed Δ{tilde over (ω)} max and theelapsed time “t” from the start of engagement of the clutch when thedefined clutch synchronizing time is larger than the allowable clutchsynchronizing time;

FIG. 11 is a flowchart of a control program executed at the controlportion of FIG. 1 for the engine start control according to the secondembodiment;

FIG. 12 is a graph, the vertical axis thereof indicating the clutch heatgeneration amount Q and the horizontal axis thereof indicating theclutch synchronizing time Tst, wherein the graph shows the relationshipbetween the allowable clutch heat generation amount Qtmax and the actualclutch heat generation amount Qr and the clutch synchronizing time Tst;

FIG. 13A is a graph, the horizontal axis thereof indicating the elapsedtime “t” from the start of engagement of the clutch and the verticalaxis thereof indicating the clutch difference rotation speed Δ{tildeover (ω)}, wherein the graph shows the relationship between theallowable clutch difference rotation speed Δ{tilde over (ω)} max and theelapsed time “t” from the start of engagement of the clutch when the“standard curvature” is equal to or less than the “allowable curvature”;

FIG. 13B is a graph, the horizontal axis thereof indicating the elapsedtime “t” from the start of engagement of the clutch and the verticalaxis thereof indicating the clutch difference rotation speed Δ{tildeover (ω)}, wherein the graph shows the relationship between theallowable clutch difference rotation speed Δ{tilde over (ω)} max and theelapsed time “t” from the start of engagement of the clutch when the“standard curvature” is larger than the “allowable curvature”;

FIG. 14 is a flowchart of a control program executed at the controlportion of FIG. 1 for the engine start control according to the thirdembodiment;

FIG. 15 is a graph, the vertical axis thereof indicating the clutch heatgeneration amount Q and the horizontal axis thereof indicating thecurvature, wherein the graph shows the relationship between theallowable clutch heat generation amount Qtmax and the actual clutch heatgeneration amount Qr and the curvature;

FIG. 16 is a skeleton view indicating the structure of the hybrid drivedevice according to a fourth embodiment of the invention; and,

FIG. 17 is a block diagram of PID (Proportional-Integral-Derivative)control embodiment which controls the clutch difference rotation speedΔ{tilde over (ω)} r.

EMBODIMENTS FOR IMPLEMENTING INVENTION

(Structure of Hybrid Drive Device)

The embodiment (First embodiment) of the hybrid drive device 100 will beexplained with reference to the attached drawings. It is noted here thatthe broken line indicated in FIG. 1 indicates the informationtransmittal route for various information and the chain line indicatesthe transmittal route for electricity. The hybrid vehicle (hereinafterreferred to as just “vehicle”) is equipped with the hybrid drive device100. The hybrid drive device 100 according to this embodiment includesan engine EG, a first motor/generator MG1, a second motor/generator MG2,a planetary gear mechanism 10, a clutch 20, a first inverter 31, asecond inverter 32, a battery 33, an actuator 50 and a control portion40. It is noted here that hereinafter the expression of the state “underclutch being in engagement” means the state of clutch 20 from adisengaged state to a state that the clutch is in connected state.

The engine EG includes a gasoline engine or diesel engine using a fuelof hydrocarbon system such as gasoline or light gas and applies arotation drive force to the drive wheels Wl and Wr. The rotation driveforce is outputted from the engine EG to an output shaft EG-1 based on acontrol signal outputted from the control portion 40. An engine rotationspeed sensor EG-2 is provided in the vicinity of the output shaft EG-1.The engine rotation speed sensor EG-2 detects the engine rotation speed{tilde over (ω)} e which corresponds to the rotation speed of the outputshaft EG-1. The detected signal is outputted to the control portion 40.The engine EG is equipped with a water temperature sensor EG-3 whichdetects the temperature “te” of a coolant for cooling the engine EG andoutputs the detected signal to the control portion 40. Further, theengine EG is equipped with a fuel injection device (not shown) forinjecting fuel to the suction port and each cylinder of the engine EG.Further, when a gasoline type engine is used as the engine EG, anignition plug (not shown) is provided at each cylinder.

The clutch 20 is disposed between the output shaft EG-1 and an inputshaft 51 of the planetary gear mechanism 10 and connects or disconnectsthe output shaft EG-1 and the input shaft 51 to electrically control atransmission of transmitting torque therebetween. Any type clutch can beused as long as such control can be performed. According to thisembodiment, the clutch 20 is of dry-type, single plate, normally closedtype clutch and includes a flywheel 21, a clutch disc 22, a clutch cover23, a pressure plate 24 and a diaphragm spring 25. The flywheel 21includes a disc-shaped plate having a predetermined mass. The flywheel21 is connected to the output shaft EG-1 and is rotatable unitarytherewith. The clutch disc 22 is of a disc plate shape and a frictionmember 22 a is provided on the outer brim portion of the disc and facesto the flywheel 21 and is engageable with or detachable from theflywheel 21. The friction member 22 a includes a so-called clutch liningand is formed by a metal made aggregate and a synthetic resin-madebinder for connecting the aggregate. The clutch disc 22 is connected tothe input shaft 51 and rotates unitary therewith.

The clutch cover 23 is formed by a cylindrical portion 23 a connected tothe outer brim portion of the flywheel 21 provided at the outerperipheral side of the clutch disc 22 and an annular plate shaped sidewall 23 b extending inwardly in a radial direction from the end portionof the cylindrical portion 23 a opposite to the connecting portion withthe flywheel 21. The pressure plate 24 is of annular shape and faces tothe clutch disc 22 at the opposite side to the facing surface with theflywheel 21 and is engageable with or disengageable from the clutch disc22.

The diaphragm spring 25 is a so-called dish spring and a diaphragminclined in a thickness direction is formed thereon. At the centralportion of the diaphragm spring 25 in a radial direction is in contactwith the inner brim portion of a side peripheral wall 23 b of the clutchcover 23 and the outer brim portion of the diaphragm spring 25 is incontact with the pressure plate 24. The diaphragm spring 25 pressurizesthe clutch disc 22 onto the flywheel 21 through the pressure plate 24.Under such pressurized condition, the friction member 22 a of the clutchdisc 22 is pressed by the flywheel 21 and the pressure plate 24 and theclutch disc 22 and the flywheel 21 are rotated together by the frictionforce generated between the friction member 22 a and the flywheel 21 andthe pressure plate 24 to thereby connect the output shaft EG-1 and theinput shaft 51.

A temperature sensor 26 is provided within a housing (not shown) whichaccommodates the clutch 20. The temperature “Th” in the housing detectedby the temperature sensor 26 is inputted to the control portion 40.

The actuator 50 varies the transmitting torque of the clutch 20 bydriving the clutch 20. The actuator 50 presses the inner brim portion ofthe diaphragm spring 25 or releases the pressurization thereon based onthe instructions from the control portion 40. An electric type or ahydraulic type may be used for the actuator 50. When the actuator 50presses the inner brim portion of the diaphragm spring 25 towards theflywheel 21 side, the diaphragm spring 25 is deformed and the outer brimportion thereof is deformed in a direction separating from the flywheel21. Then the deformation of the diaphragm spring 25 gradually decreasesthe pressing force of the flywheel 21 and the pressure plate 24 to theclutch disc 22 and finally the transmitting torque between the clutchdisc 22 and the flywheel 21 and the pressure plate 24 is decreasedthereby to release the connection between the output shaft EG-1 and theinput shaft 51. Thus, the control portion 40 randomly varies thetransmitting torque between the clutch disc 22 and the flywheel 21 andthe pressure plate 24 by actuating the actuator 50.

The first motor/generator MG-1 is operated as a motor for applyingrotation drive force to the drive wheels Wl and Wr, and at the same timeis used as a generator which converts a kinetic energy of the vehicle tothe electric energy. The first motor/generator MG1 is formed by a firststator St1 fixed to a case (not shown) and a first rotor Ro1 rotatablyprovided at the inner peripheral side of the first stator St1. It isnoted that a rotation speed sensor MG1-1 is provided in the vicinity ofthe first rotor Ro1 which detects the rotation speed {tilde over (ω)}MG1 r of the first motor/generator MG1 (first rotor Ro1) and outputs thedetected signal to the control portion 40.

The first inverter 31 is electrically connected to the first stator St1and the battery 33. The first inverter 31 is connected to the controlportion 40 and establishes communication therebetween. The firstinverter 31 converts the DC current supplied from the battery 33 intothe AC current by increasing the voltage based on the control signalfrom the control portion 40 and the converted AC current is supplied tothe first stator S to generate the rotation drive force by the firstmotor/generator MG1 thereby the first motor/generator MG1 being used asa motor. The first inverter 31 controls the first motor/generator MG1 tofunction as a generator based on the control signal from the controlportion 40 and the AC current generated at the first motor/generator MG1is converted into the DC current and at the same time the voltage isdecreased thereby charging the battery 33.

The second motor/generator MG2 is operated as a motor for applyingrotation drive force to the drive wheels Wl and Wr, and at the same timeis used as a generator which converts a kinetic energy of the vehicle tothe electric energy. The second motor/generator MG2 is formed by asecond stator St2 fixed to a case (not shown) and a second rotor Ro2rotatably provided at the inner peripheral side of the second statorSt2.

The second inverter 32 is electrically connected to the second statorSt2 and the battery 33. The second inverter 32 is connected to thecontrol portion 40 and establishes communication therebetween. Thesecond inverter 32 converts the DC current supplied from the battery 33into the AC current by increasing the voltage based on the controlsignal from the control portion 40 and the converted AC current issupplied to the second stator St2 to generate the rotation drive forceby the second motor/generator MG2 thereby the second motor/generator MG2being used as a motor. The second inverter 32 controls the secondmotor/generator MG2 to function as a generator based on the controlsignal from the control portion 40 and the AC current generated at thesecond motor/generator MG2 is converted into the DC current and at thesame time the voltage is decreased, thereby charging the battery 33.

The planetary gear mechanism 10 divides the rotation drive force of theengine EG into the first motor/generator MG1 side and a differentialmechanism DF side, which will be explained later and is formed by a sungear 11, a planetary gear 12, a carrier 13 and a ring gear 14. The sungear 11 is connected to the first rotor Ro1 for unitary rotationtherewith. The planetary gear 12 is provided at the periphery of the sungear 11 with a plurality of numbers and engages with the sun gear 11.The carrier 13 rotatably (rotation) supports the plurality of planetarygears 12. The carrier 13 is connected to the input shaft 51 for unitaryrotation therewith. The ring gear 14 is of ring shaped and is formedwith a plurality of inner gears 14 a at the inner peripheral surfacethereof. An output gear 14 b is provided at the outer peripheral surfaceof the ring gear 14. The plurality of inner gearsl4 a is in engagementwith the plurality of planetary gears 12.

A reduction gear 60 is formed by a first gear 61, a second gear 62 and aconnecting shaft 63. The first gear 61 is in engagement with the outputgear 14 b of the ring gear 14 and at the same time in engagement with anoutput gear 71 which unitary rotates with the second rotor Ro2. Thesecond gear 62 is in connection with the first gear 61 through theconnecting shaft 63 and rotates unitary with the first gear 61. It isnoted that the second gear 62 has a diameter smaller than the diameterof the first gear 61 and the number of teeth of the second gear 62 issmaller than the number of the first gear 61. The second gear 62 is inengagement with the input gear 72.

The differential mechanism DF delivers the rotation drive forcetransmitted to the input gear 72 to drive shafts 75 and 76, which arerespectively connected to the drive wheels Wl and Wr. As explainedabove, the input shaft 51 is rotatably connected to the drive wheels Wland Wr through the planetary gear mechanism 10, the reduction gear 60,the differential mechanism DF and the drive axles 75 and 76. It is notedthat no second clutch, formed separately from the clutch 20 existsbetween the engine EG and the clutch 20. Further, it is noted that nosecond clutch formed separately from the clutch 20 exists between theclutch 20 and the drive wheels Wl and Wr.

The control portion 40 centrally controls the hybrid drive device 100and includes an ECU. The ECU is equipped with a memory portion formed byan input/output interface, CPU, RAM, ROM and non-volatile memoryrespectively connected with one another through bus lines. The CPUexecutes the program corresponding to the flowchart illustrated in FIGS.3, 4, 5, 8, 9, 11 and 14. The RAM temporally memorizes variablesnecessary for executing the program. The memory portion memorizes thedetected values from the various sensors and also memorizes the program.The control portion 40 may be formed by one single ECU or may be formedby a plurality of ECUs.

The control portion 40 obtains the information on acceleration openingdegree Ac which indicates the absolute value of the operating amount ofan acceleration pedal 81 detected by an acceleration sensor 82. Thecontrol portion 40 further obtains the vehicle wheel speeds Vr and Vlfrom the vehicle wheel sensors 85 and 86 which detect rotation speed ofeach of the vehicle wheels Wl and Wr (not necessarily be the drivewheels) and then the vehicle speed V can be calculated based on theobtained vehicle wheel speeds Vr and Vl. The control portion 40calculates the “required drive force” based on the acceleration openingdegree Ac and the vehicle speed V. The control portion 40 obtains theinformation on brake opening degree Bk which indicates the absolutevalue of the operating amount of a brake pedal 83 detected by a brakesensor 84. The control portion 40 calculates the “required brakingforce” based on the brake opening degree Bk. The control portion 40calculates the input shaft rotation speed {tilde over (ω)} i whichcorresponds to the rotation speed of the input shaft 51 (carrier 13)based on the rotation speed {tilde over (ω)} MG1 r of the firstmotor/generator MG1 inputted from the rotation speed sensor MG1-1, therotation speed {tilde over (ω)} MG2 r of the second motor/generator MG2(calculated from the vehicle speed V) and the number of teeth betweenthe sun gear 11 and the inner gear 14 a.

(Explanation of Electric Running Mode and Split Running Mode)

Next, using the velocity diagram illustrated in FIG. 2, the “Electricrunning mode” and the “Split running mode” will be explained. Thevehicle is either in “electric running mode” or in “split running mode”and both modes are switchable during the vehicle in a running state. The“electric running mode” means the mode in which the vehicle is driven bythe rotation drive force of at least one of the first and the secondmotor/generators MG1 and MG2, whereas the “split running mode” means themode in which the vehicle is driven by the rotation drive force of atleast one of the first and the second motor/generators MG1 and MG2 andthe rotation drive force of the engine EG and the other of the first andthe second motor/generators MG1 and MG2 generates electricity (undergeneration operation).

As shown in the diagram of FIG. 2, the vertical axis indicates therotation speed of each rotation element. The area upper than the valuezero in FIG. 2 indicates the area where the rotation is in a positivedirection and the area lower than the value zero indicates the areawhere the rotation is in a negative direction. In FIG. 2, the symbol “s”indicates the rotation speed of the sun gear 11, “ca” indicates therotation speed of the carrier 13 and “r” indicates the rotation speed ofthe ring gear 14. In other words, the symbol “s” indicates the rotationspeed of the first motor/generator MG1, “ca” indicates the rotationspeed of the input shaft 51 and “r” indicates the rotation speedproportional to the rotation speed of the second motor/generator MG2 andthe rotation speed of the drive wheels Wl and Wr (vehicle speed). It isnoted that when the clutch 20 is completely engaged, the rotation speed“ca” becomes the same speed as the rotation speed of the output shaftEG-1 of the engine EG. Assuming that the distance between the verticallines “s” and “ca” is one (1), the distance between the vertical lines“ca” and “r” becomes the gear ratio “λ” of the planetary gear mechanism10 (ratio of the number of teeth between the sun gear 11 and the innergear 14 a: the number of teeth of sun gear 11/the number of teeth ofinner gear 14 a). As explained, the first motor/generator MG1 (firstrotor Ro1), the input shaft 51 and the second motor/generator MG2 arerotated mutually associated with one another.

Under the battery being in sufficiently charged state and the requireddrive force is sufficiently obtained from the rotation drive force fromthe first and the second motor/generators MG1 and MG2 only, the vehicleis driven under the “electric running mode”.

Under the “electric running mode”, when the vehicle is driven by therotation drive force only from the second motor/generator MG2, thecontrol portion 40 controls the actuator 50 to disconnect the clutch 20.Thus the engine EG and the input shaft 51 are disconnected. The controlportion 40 sends the control signal to the second inverter 32 to drivethe second motor/generator MG2 to generate the “required drive force”.Under this state, as shown by the solid line in FIG. 2A, the secondmotor/generator MG2 rotates in the positive direction. The engine EG isstopped due to the disconnection from the input shaft 51 (the enginerotation speed {tilde over (ω)} e is zero) (the state of point “1” inFIG. 2A). When the vehicle is driven only by the rotation drive force ofthe second motor/generator MG2, the clutch 20 is in disconnected state,and therefore, the input shaft 51 is freely rotatable. (State of point“5” in FIG. 2A). Therefore, the rotation drive force from the secondmotor/generator MG2 transmitted to the ring gear 14 is idly rotatedwithin the planetary gear mechanism 10 due to the free rotation of theinput shaft 51. Thus, the first motor/generator MG1 does not rotate (therotation speed {tilde over (ω)} MG1 r is zero) (State of point “6” inFIG. 2A). Since the first motor/generator MG1 does not rotate, anyrotation loss derived from the rotation of the first motor/generator MG1(inertia torque of the first rotor Ro1) can be prevented to saveelectric energy (to improve electricity consumption of the vehicle).

When the vehicle is running under the “electric running mode” and therequired drive force is not sufficient by the rotation drive force ofthe second motor/generator MG2 only, the control portion 40 outputs thecontrol signal to the actuator 50 to engage the clutch 20 forestablishing connection between the output shaft EG-1 and the inputshaft 51. At the same time the control portion 40 outputs the controlsignal to the first and the second inverters 31 and 32 to drive thefirst and the second motor/generators MG1 and MG2 to obtain the requireddrive force for the vehicle. Under this state, as shown by the brokenline in FIG. 2A, the first motor/generator MG1 is rotated in thenegative direction (The state of point “2” in FIG. 2A) and the secondmotor/generator MG2 is rotated in the positive direction and the engineEG is stopped. (The state of point “3” in FIG. 2A). Under this state,the friction torque of the engine EG, which is a negative torque,functions as a reaction force receiver for supporting the carrier 13.Therefore, the maximum rotation drive force that the firstmotor/generator MG1 can output is limited to the rotation drive forcethat the rotation drive force transmitted to the input shaft 51 by thefirst motor/generator MG1 becomes equal to or less than the frictiontorque of the engine EG.

When the required drive force is not sufficient only by the rotationdrive force generated by the first and the second motor/generators MG1and MG2 or when the battery is not sufficiently charged, the vehicle isdriven under the “split running mode”.

Under the “split running mode”, the control portion 40 controls theactuator 50 to actuate the clutch 20 to be in engagement state and atthe same time the control portion 40 controls the engine EG to generatea predetermined rotation drive force. Thus, the engine EG and the inputshaft 51 are connected and the engine rotation drive force is inputtedto the carrier 13 and the engine rotation drive force transmitted to thecarrier 13 is divided into two directions and transmitted to the sungear 11 and the ring gear 14, respectively. Thus, the engine rotationdrive force is delivered to the first motor/generator MG1 and the drivewheels Wr and Wl.

Under the “split running mode”, the engine EG is maintained to a highlyefficient state (high efficient state in fuel consumption ratio). Underthis state, as shown by the chain line in FIG. 2A, the firstmotor/generator MG1 receives the divided rotation drive force from theengine EG and rotates in the positive direction (state of point “4” inFIG. 2A) and generates the electricity. Thus, the first motor/generatorMG1 outputs a motor/generator torque in a negative direction to the sungear 11. In other words, the first motor/generator MG1 functions as areaction force receiver which supports the reaction force of enginetorque TE. Accordingly, the rotation drive force of the engine EG isdistributed to the ring gear 14 and eventually to the drive wheels Wland Wr. The second motor/generator MG2 is driven by the electric currentwhich the first motor/generator MG1 generates and the electric currentwhich is supplied from the battery 33 to drive the drive wheels Wl andWr.

It is noted here that when the control portion 40 judges that theacceleration pedal 81 has been released (acceleration opening degree“Ac” is zero) or judges that the brake pedal 83 has been depressed (thebrake opening degree Bk is larger than zero), a regeneration brakingoperation is executed. Under the “regeneration braking” operation, thecontrol portion 40 generally controls the actuator 50 to actuate theclutch 20 to be in a disconnected state. Then the control portion 40outputs the control signal to the second inverter 32 and theregeneration braking force is generated at the second motor/generatorMG2. At this timing, the second motor/generator MG2 generates therotation drive force in a negative direction and the current generatedat the second motor/generator MG2 is charged to the battery 33.Accordingly, the regeneration braking is executed when the clutch 20 isdisconnected and the vehicle kinetic energy is not wastefully consumeddue to the friction torque of the engine EG. It is noted that under thebattery 33 being fully charged state, when the so-called engine brake isused in addition to the friction brake for generating the braking force,the control portion 40 controls the actuator 50 to actuate the clutch 20to be brought into engagement state thereby rotating the engine EG toutilize the engine friction toque (so-called engine brake) fordeceleration of the vehicle.

(Clutch Control)

Hereinafter, the clutch control will be explained with reference to theflowchart shown in FIG. 3. When the vehicle is in a runnable state, atthe step S11 and when the control portion 40 judged that the engine isstopped (S11: YES), the control portion 40 advances the program to thestep S12 and judged that the engine is not stopped (S11: NO), thecontrol portion advances the program to the step S15.

At the step S12, when the control portion 40 judged that the enginestart condition has been established (S12: YES), the program goes to thestep S13 and judged that the engine start condition has not beenestablished (S12: NO), the control portion 40 returns the program to thestep S11. It is noted that when the control portion 40 judged that theremaining amount of the battery 33 has dropped, or the required driveforce is not sufficient by the generation by the first and the secondmotor/generators MG1 and MG2, the engine start condition is deemed to beestablished.

At the step S13, the control portion 40 starts execution of the enginestart control. This engine start control will be explained later withreference to the flowchart in FIG. 4. After the processing of the stepS13 finished, the program returns to the step S11.

At the step S15, when the control portion 40 judged that the engine EGstop condition has been established (S15: YES), the program goes to thestep S16 and judged that the engine EG stop condition has not beenestablished (S15: NO), the program returns to the step S11. It is notedthat when the control portion 40 judges that the battery remainingamount is sufficient, or that the required drive force is sufficient bythe generation by the first and the second motor/generators MG1 and MG2,or when the engine EG is stopped to perform the regeneration barkingoperation, the engine EG stop condition is deemed to be established.

At the step S16, the control portion 40 outputs the control signal tothe actuator 50 to disconnect the clutch 20 and the program goes to thestep S17. At the step S17, the control portion 40 outputs the controlsignal to the engine EG to stop the fuel injection by the fuel injectiondevice and to stop igniting operation by the ignition device thereby tostop the engine EG. Then the program returns to the step S11.

(Engine Start Control)

The engine start control will be explained hereinafter with reference tothe flowchart shown in FIG. 4. When the engine start control isinitiated, at the step S61, the control portion 40 calculates theallowable clutch difference rotation speed Δ{tilde over (ω)} _(—)0max atthe start of engagement which corresponds to the allowable clutch 20difference rotation speed at the start of the clutch 20 being engaged.It is noted here that the clutch 20 difference rotation speed means thedifference in rotation speed between the rotation speed of the inputshaft 51 and the engine rotation speed {tilde over (ω)} e (output shaftEG-1). Further, upon initiation of the engine start control, engine isstopped (engine rotation speed {tilde over (ω)} e being zero), the valueof the allowable clutch difference rotation speed Δ{tilde over (ω)}_(—)0max at the start of engagement represents the allowable clutchdifference rotation speed {tilde over (ω)} i_(—)0max at the start ofengagement which corresponds to the rotation speed of the input shaft 51at the start of engagement.

The allowable clutch difference rotation speed calculation processingwhich is the sub-routine of the step S61 in FIG. 4 will be explainedwith reference to FIG. 5. When the allowable clutch difference rotationspeed calculation processing is initiated, at the step S61-1, the clutchtemperature Tcrt which corresponds to the current temperature of thefriction member 22 a is obtained. According to this embodiment, theclutch temperature Tcrt is the temperature of the friction member 22 a.More specifically, the control portion 40 obtains the clutch temperatureTcrt which corresponds to the current temperature of the friction member22 a by estimation based on the housing inside temperature Th detectedby the temperature sensor 26, integrated value of the heat generationamount of the friction member 22 a and the integrated value of the heatdissipation amount of the friction member 22 a and the clutch 20 as awhole. The heat generation amount of the friction member 22 a iscalculated by the clutch difference rotation speed Δ{tilde over (ω)} rwhich corresponds to the difference rotation speed of the clutch 20being in engagement (difference in rotation speed between the enginerotation speed toe and the input shaft rotation speed {tilde over (ω)}i) and the clutch transmitting torque Tcr. After the processing at thestep S61-1 finished, the program goes to the step S61-2.

At the step S61-2, the control portion 40 calculates the allowableclutch heat generation amount Qtmax which corresponds to the heatgeneration amount that is allowed when the clutch 20 is engaged.According to this embodiment, the heat generation amount allowable forthe operation of the clutch 20 means the heat generation amountallowable at the friction member 22 a. In detail, the allowable clutchheat generation amount Qtmax is obtained by substituting the clutchtemperature Tcrt (temperature of the friction member 22 a) obtained atthe step S61-1 into the following formula (1): wherein:

Qtmax=K(Tmax −Tcrt)   (1)

-   Qtmax: allowable clutch heat generation amount-   K: coefficient for converting the temperature difference into the    heat generation amount at the clutch 20 (friction member 22 a)-   Tmax: clutch allowable temperature (allowable temperature of    friction member 22 a)-   Tcrt: current clutch temperature (current friction member 22 a    temperature).

It is noted that the clutch allowable temperature Tmax is thetemperature lower than the upper temperature limit by a predeterminedvalue, i.e., lower than the temperature of the binder upper temperaturelimit by a predetermined value. When the step S61-2 finished, theprogram goes to the step S61-3.

At the step S61-3, the control portion 40 estimates the oil temperatureof the engine EG based on the coolant temperature to of the engine EGdetected by the water temperature sensor

EG-3. Then the control portion 40 calculates the friction torque Te ofthe engine EG based on the oil temperature of the engine EG and advancesthe program to the step S61-4.

At the step S61-4, the control portion 40 calculates the relationship asa quadratic function between the clutch difference rotation speedΔ{tilde over (ω)} _(—)0 at the start of engagement and the actual clutchheat generation amount Qr by inputting the friction torque Te calculatedat the step S61-3, engine inertia le and the target clutch synchronizingtime Tst into the mapping data or the calculating formula whichillustrates the relationship thereof with the friction torque of theengine EG, engine inertia, target clutch synchronizing time, actualclutch heat generation amount Qr and the clutch difference rotationspeed Δ{tilde over (ω)} (See FIG. 6). It is noted that the engineinertia le is an inertia moment of the various rotation members of theengine EG. The rotation members of the engine EG include crankshaft, conrod, piston, output shaft EG-1, flywheel 21, clutch cover 23, pressureplate 24 and diaphragm spring 25. The engine inertia is set in advance.The target clutch synchronizing time is an elapsed time from the startof engagement of the clutch to the completion of the synchronization ofthe output shaft EG-1 and the input shaft 51. The target clutchsynchronizing time Tst is set in advance considering the shocksgenerated upon clutch engagement. The actual clutch heat generationamount Qr is the heat amount of the clutch 20 being in engagement andaccording to the embodiment, the heat generation amount of the frictionmember 22 a under the clutch being in engagement. Since the engine EG isstopped upon the start of engagement of the clutch, the clutchdifference rotation speed Δ{tilde over (ω)} corresponds to the inputrotation speed {tilde over (ω)} i.

The clutch difference rotation speed Δ{tilde over (ω)} under the clutchbeing in engagement is represented as the following formula (11):

Δ{tilde over (ω)} =−(Δ{tilde over (ω)} 0/Tst)×t+Δ{tilde over (ω)} 0  (11)

-   Δ{tilde over (ω)} : clutch difference rotation speed-   Tst: target clutch synchronizing time-   t: elapsed time of the clutch 20 from the start of engagement-   Δ{tilde over (ω)} _(—)0: clutch difference rotation speed at the    start of engagement of the clutch

As shown above, when the clutch difference rotation speed Δ{tilde over(ω)} under the clutch being in engagement is set as above formula (11),the relationship between the clutch difference rotation speed at thestart of engagement of the clutch and the actual clutch heat generationamount Qr becomes the quadratic function as shown in FIG. 6.

It is noted that the mapping data or the calculation formula is set tobe a quadratic function in which the actual heat generation amount Qrbecomes large as the friction torque Te becomes large with respect tothe relationship with the clutch difference rotation speed Δ{tilde over(ω)} _(—)0 at the start of engagement (the quadratic function becomesmore in the quadratic function f1 side than in the quadratic function f3side). Further, the mapping data or the calculation formula is set to bea quadratic function in which the actual heat generation amount Qrbecomes large as the engine inertia le becomes large with respect to therelationship with the clutch difference rotation speed Δ{tilde over (ω)}_(—)0 at the start of engagement (the quadratic function becomes more inthe quadratic function f1 side than in the quadratic function f3 side).Still further, the mapping data or the calculation formula is set to bea quadratic function in which the actual heat generation amount Qrbecomes large as the target clutch synchronizing time Tst becomes largewith respect to the relationship with the clutch difference rotationspeed Δ{tilde over (ω)} _(—)0 at the start of engagement (the quadraticfunction becomes more in the quadratic function f1 side than in thequadratic function f3 side). After the processing of the step S61-4, theprogram goes to the step S61-5.

At the step S61-5, the control portion 40 calculates the allowableclutch difference rotation speed Δ{tilde over (ω)} _(—)0max at the startof engagement based on the allowable clutch heat generation amount Qtmaxcalculated at the step S61-2 and the relationship between the clutchdifference rotation speed Δ{tilde over (ω)} _(—)0 at the start ofengagement and the actual heat generation amount. More specifically inFIG. 6, the allowable clutch difference rotation speed Δ{tilde over (ω)}_(—)0max at the start of engagement is calculated from the intersectionpoint between the allowable clutch heat generation amount Qtmax which isrepresented as the direct function and the relationship between theclutch difference rotation speed Δ{tilde over (ω)} _(—)0 at the start ofengagement and the actual clutch heat generation amount Qr which isrepresented as the quadratic function.

At the step S61-5, the control portion 40 calculates the allowableclutch difference rotation speed Δ{tilde over (ω)} max (bold broken linein FIG. 7) by substituting the allowable clutch difference rotationspeed Δ{tilde over (ω)} _(—)0max at the start of engagement , the targetclutch synchronizing time Tst and the elapsed time “t” from the start ofthe clutch 20 engagement into the following formula (12):

Δ{tilde over (ω)} max=−(Δ{tilde over (ω)} _(—)0max/Tst) ×t+Δ{tilde over(ω)} _(—)0max   (12)

-   Δ{tilde over (ω)} max: allowable clutch difference rotation speed-   Δ{tilde over (ω)} _(—)0max: allowable clutch difference rotation    speed at the start of engagement-   Tst: target clutch synchronizing time-   “t”: elapsed time from the start of engagement of the clutch 20.

After the processing at the step S61-5, the allowable clutch differencerotation speed at the start of engagement calculation process ends (theprocess of the step S61 in FIG. 4 ends) and the program goes to the stepS62 in FIG. 4.

At the step S62, when the control portion 40 judged that the currentclutch difference rotation speed Δ{tilde over (ω)} r is equal to or lessthan the allowable clutch difference rotation speed Δ{tilde over (ω)}_(—)0max at the start of engagement (S62: YES), the program goes to thestep S63 and when the control portion 40 judged that the current clutchdifference rotation speed Δ{tilde over (ω)} r is more than the allowableclutch difference rotation speed Δ{tilde over (ω)} _(—)0max at the startof engagement (S62: NO), the program goes to the step S64. It is notedthat the engine EG (output shaft EG-1) rotation speed is zero before theengine starts and accordingly, the current clutch difference rotationspeed Δ{tilde over (ω)} r equals to the current input shaft rotationspeed {tilde over (ω)} i.

At the step S63, the control portion 40 sets the current input shaftrotation speed {tilde over (ω)} i to the target input shaft rotationspeed {tilde over (ω)} it_(—)0 at the start of engagement and theprogram goes to the step S67.

At the step S64, the control portion 40 sets the allowable input shaftrotation speed {tilde over (ω)} i_(—)0max at the start of engagement tothe target input shaft rotation speed {tilde over (ω)} it_(—)0 at thestart of engagement. As explained above, the allowable input shaftrotation speed {tilde over (ω)} i_(—)0max at the start of engagement isthe same value as the allowable clutch difference rotation speed Δ{tildeover (ω)} _(—)0max at the start of engagement. After the processing atthe step S64 finished, the program goes to the step S65.

At the step S65, the control portion 40 outputs the control signal tothe first inverter 31 and rotationally controls the rotation of thefirst motor/generator MG1 so that the input shaft rotation speed {tildeover (ω)} l becomes the target input shaft rotation speed {tilde over(ω)} it_(—)0 at the start of engagement (allowable clutch differencerotation speed Δ{tilde over (ω)} _(—)0max at the start of engagement).First, the control portion 40 calculates the target rotation speed{tilde over (ω)} MG1 t of the first motor/generator MG1, in which theinput shaft rotation speed {tilde over (ω)} i becomes the target inputshaft rotation speed {tilde over (ω)} it_(—)0 at the start of engagementwhich was set at the step S64. More specifically, the control portion 40calculates the target rotation speed {tilde over (ω)} MG1 t bysubstituting the target input shaft rotation speed {tilde over (ω)}it_(—)0 at the start of engagement and the rotation speed ωr of the ringgear 14 into the following formula (2).

ωMG1t={(λ+1)×ωit _(—)0−ωr}/λ  (2)

-   ωMG1 t: target rotation speed of the first motor/generator MG1:-   λ: gear ratio of the planetary gear mechanism 10 ((the number of    teeth of the sun gear 11)/(the number of teeth of the inner gear 14    a)):

ωit⁻0: target input shaft rotation speed at the start of engagement(rotation speed of the carrier 13):

-   ωr: the rotation speed of the ring gear 14.

It is noted that since the rotation speed ωr of the ring gear 14 isproportional to the vehicle speed V and the rotation speed of the secondmotor/generator MG2, the control portion 40 calculates the rotationspeed ωr of the ring gear 14 based on the vehicle speed V and therotation speed of the second motor/generator MG2. Or, alternatively therotation speed ωr of the ring gear 14 may also be obtained by directlydetecting the rotation speed ωr of the ring gear 14.

Next, the control portion 40 executes a PID control (feedback control)so that the rotation speed ωMG1 r of the first motor/generator MG1agrees with the above calculated target rotation speed ωMG1 t byoutputting a control signal to the first inverter 31 based on therotation speed ωMG1 r of the first motor/generator MG1 detected by therotation speed sensor MG1-1. For example, as shown with the solid linein FIG. 2B, under the first motor/generator MG1 being stopped (rotationspeed is zero), which is indicated at the point 1 in FIG. 2B, when thecurrent input shaft rotation speed {tilde over (ω)} i (point 2 in FIG.2B) is larger than the target input shaft rotation speed {tilde over(ω)} it_(—)0 at the start of engagement (point 3 in FIG. 2B), thecontrol portion 40 controls the rotation speed {tilde over (ω)} MG1 r ofthe first motor/generator MG1 to the negative rotation side targetrotation speed {tilde over (ω)} MG1 t (point 4 in FIG. 2B) so that therotation speed of the carrier 13 becomes the target input shaft rotationspeed {tilde over (ω)} it_(—)0 at the start of engagement (point 3 inFIG. 2B). Thus, the clutch 20 is controlled to the allowable clutchdifference rotation speed Δ{tilde over (ω)} _(—)0max at the start ofengagement. After the processing at the step S65 finished, the programgoes to the step S66.

At the step S66, when the control portion judged that the current inputshaft rotation speed ωi is the target input shaft rotation speed {tildeover (ω)} it_(—)0 at the start of engagement (S66: YES), the programgoes to the step S67 and when the control portion 40 judged that thecurrent input shaft rotation speed ωi is not the target input shaftrotation speed {tilde over (ω)} it_(—)0 at the start of engagement (S66:NO), the program returns to the step S65.

At the step S67, the control portion 40 calculates the target clutchtransmitting torque Tct which corresponds to the transmitting torque tobe targeted under the clutch 20 being in engagement. More specifically,the control portion 40 calculates the target clutch transmitting torqueTct by substituting the engine friction torque Te calculated at the stepS61-3, the engine inertia le, the target input shaft rotation speed{tilde over (ω)} it_(—)0 at the start of engagement and the targetclutch synchronizing time Tst into the following formula (3) below:

Tct=Te+le·ωit _(—)0/Tst   (3)

-   Tct: target clutch transmitting torque:-   Te: friction torque of the engine EG:-   le: engine inertia:-   ωit_(—)0: target input shaft rotation speed at the start of    engagement (allowable clutch difference rotation-   speed at the start of engagement):-   Tst: target clutch synchronizing time.

Using the formula (3) above, the target clutch transmitting torque Tctcan be obtained wherein the engine EG rotation speed becomes the targetinput shaft rotation speed ωit_(—)0 at the start of engagement after thetarget clutch synchronizing time Tst elapsed from the start ofengagement of the clutch 20. After the processing at the step S67finished, the program goes to the step S68.

At the step S68, by outputting a control signal to the actuator 50, thecontrol portion 40 executes the feedback control so that the clutchtransmitting torque generated at the clutch 20 becomes the target clutchtransmitting torque Tct calculated at the step S67. It is noted that thecontrol portion 40 calculates the clutch temperature Tcrt in a mannersimilar to the manner processed at the step S61-1 in FIG. 5 andcalculates the friction force between the friction member 22 a and theflywheel 21 and the pressure plate 24 based on the clutch temperatureTcrt, the difference rotation speed between the engine rotation speed{tilde over (ω)} e and the input shaft rotation speed {tilde over (ω)} iand the clutch pushing load. Then the control portion 40 controls theclutch transmitting torque by feedback control to output the controlsignal to the actuator 50 based on the change of the friction force. Theclutch pushing load is a load received by the clutch disc 22 upon beingpressurized by the flywheel 21 and the pressure plate 24 and the controlportion 40 can confirm the clutch pushing load by the control signaloutputted to the actuator 50.

Thus, the control portion 40 calculates the target clutch transmittingtorque Tct based on the formula (3) above at the step S67 and at thestep S68, by executing the above control, the engine EG rotation speedcan be obtained as shown in the formula (4) below:

{tilde over (ω)} e={tilde over (ω)} it _(—)0/Tst *t   (4)

-   {tilde over (ω)} e:engine EG rotation speed-   {tilde over (ω)} it_(—)0: target input shaft rotation speed at the    start of engagement (equal to the allowable clutch difference    rotation speed at the start of engagement)-   Tst: target clutch synchronizing time-   “t”:elapsed time from the start of engagement of the clutch 20.

After the process of the step S68 finished, the program goes to the stepS69.

At the step S69, the control portion 40 renews the target input shaftrotation speed {tilde over (ω)} it under the clutch 20 being inengagement by substituting the values of the target input shaft rotationspeed {tilde over (ω)} it_(—)0 at the start of engagement, the targetclutch synchronizing time Tst, the elapsed time “t” elapsed from thestart of engagement of the clutch 20, and current engine rotation speed{tilde over (ω)} e into the following formula (5):

ωit=−ωit _(—)0/Tst·t+ωe+ωit _(—)0   (5)

-   ωit: target input shaft rotation speed under the clutch 20 being in    engagement:-   ωit_(—)0: target input shaft rotation speed at the start of    engagement (allowable clutch difference rotation speed at the start    of engagement): πTst: target clutch synchronizing time:-   t: elapsed time from the start of engagement of the clutch 20:-   ωe: engine rotation speed.

By using the formula (5) above, the target input shaft rotation speedωit after renewal is calculated so that the clutch 20 is synchronized(state where the rotation difference is zero between the output shaftEG-1 and the input shaft 51) after the target clutch synchronizing timeTst elapsed from the start of engagement of the clutch. In other words,when the target input shaft rotation speedωit_(—)0 at the start ofengagement is set at the step S64, the target input shaft rotation speedωit under the clutch 20 being in engagement can be calculated accordingto the formula (5) above and accordingly, as the result as shown in FIG.7 with the bold line, the relationship between the target clutchdifference rotation speed Δωt and the elapsed time “t” from the start ofengagement of the clutch is represented as the direct function in whichthe target clutch difference rotation speed Δωt gradually decreases asthe elapsed time “t” increases.

When the engine rotation speed {tilde over (ω)} e increases as intendedfrom the start of engagement of the clutch as shown in the formula (4)above, the formula “{tilde over (ω)} it={tilde over (ω)} it_(—)0” isestablished (See broken line (1) in FIG. 7B). On the other hand, whenthe engine rotation speed {tilde over (ω)} e increases faster than theintended increase from the start of engagement of the clutch as shown inthe formula (4) above, the formula “{tilde over (ω)} it>{tilde over (ω)}it_(—)0” is established (See broken line (2) in FIG. 7B). Further, whenthe engine rotation speed {tilde over (ω)} e increases slower than theintended increase from the start of engagement of the clutch as shown inthe formula (4) above, the formula “{tilde over (ω)} it<{tilde over (ω)}it_(—)0” is established (See broken line (3) in FIG. 7B). After the stepS69 finished, the program goes to the step S70.

At the step S70, as similar to the manner executed at the step S65, thecontrol portion 40 first calculates the target rotation speed {tildeover (ω)} MG1 t of the first motor/generator MG1 in which the rotationspeed of the carrier 13 becomes the target input shaft rotation speed{tilde over (ω)} it under being in engagement calculated at the stepS69. Then the control portion 40 executes the feedback control (PID) sothat the rotation speed {tilde over (ω)} MG1 r of the firstmotor/generator MG1 becomes the above calculated target rotation speed{tilde over (ω)} MG1 t by outputting the control signal to the firstinverter 31 based on the rotation speed {tilde over (ω)} MG1 r of thefirst motor/generator MG1 detected by the rotation speed sensor MG1-1.It is noted that the input shaft rotation speed {tilde over (ω)} i canbe obtained by the following formula (6).

{tilde over (ω)} i=(λ×{tilde over (ω)} MG1r+{tilde over (ω)} r)/(1+λ)  (6)

-   {tilde over (ω)} i: input shaft rotation speed πλ: gear ratio of the    planetary gear mechanism 10 (ratio of gear teeth between the sun    gear 11 and the inner gear 14 a: the number of teeth of the sun gear    11/the number of teeth of the inner gear 14 a)-   {tilde over (ω)} MG1 r: rotation speed {tilde over (ω)} MG1 r of the    first motor/generator MG1 (first rotor Ro1)-   {tilde over (ω)} r: rotation speed of the ring gear 14.

As explained, the input shaft rotation speed {tilde over (ω)} i can berepresented as the formula (6) above and accordingly, when the vehiclespeed which has a proportional relationship with the rotation speed ofthe ring gear 14 changes, the input shaft rotation speed {tilde over(ω)} i also changes. As the result, the actual heat generation amount Qris supposed to be increased. However, the feedback control is executedat the step S70 to have the input shaft rotation speed {tilde over (ω)}i to be accorded with the target input shaft rotation speed {tilde over(ω)} it. Thus the change of actual heat generation amount due to thechange of the vehicle speed can be minimized or suppressed.

By this processing at the step S70, as shown in FIG. 7 with a fine line,the clutch difference rotation speed Δ{tilde over (ω)} r graduallydecreases along the bold line representing the target clutch differencerotation speed Δ{tilde over (ω)} t in FIG. 7 with time from the start ofengagement of the clutch 20. After the target clutch synchronizing timeTst elapsed, the value becomes zero to have the clutch 20 to be insynchronizing state. In other words, the relationship between the clutchdifference rotation speed Δ{tilde over (ω)} r and the elapsed time “t”from the start of engagement of the clutch is approximately a directfunction in which the relationship decreases as the time “t” increases.After the step S70 finished, the program goes to the step S71.

At the step S71, the control portion 40 starts the first engine startingprocess. This first engine starting process will be explained withreference to the flowchart shown in FIG. 8. When the first engine startprocess is started and when the control portion 40 judges that theengine EG has already started at the step S71-1 (S71-1; YES), the firstengine start process ends (process of the step S71 in FIG. 4 ends), thenthe program goes to the step S72 in FIG. 4 and when the control portion40 judges that the engine EG has not started at the step S71-1(S71-1;NO), the program goes to the step S71-2.

At the step S72-2, when the control portion 40 judges that the enginerotation speed ωe is judged to be equal to or more than an enginestarting rotation speed which is necessary for starting the engine EG(S71-2; YES), the program goes to the step S71-3 and judged to be lessthan the engine starting rotation speed (S71-2; NO), the first enginestart process ends (the process of step S71 of FIG. 4) and the programgoes to the step S72 of FIG. 4.

At the step S71-3, the control portion 40 injects the fuel by the fuelinjection device and at the same time ignites the plugs to start theengine EG. After the process of the step S71-3 ends, the first enginestart process ends (the process of the step S71 in FIG. 4 ends) and theprogram goes to the step S72 of FIG. 4.

At the step S72, when the control portion 40 judges that the enginerotation speed ωe and the input shaft rotation speed ωi agree with eachother (S72; YES), the program goes to the step S73 and when judged thatboth rotation speeds ωe and ωi do not agree with each other (S72; NO),the program returns to the step S68. It is noted that the state that theengine rotation speed ωe and the input shaft rotation speed ωi agreewith each other is the state that the engine rotation speed ωe and theinput shaft rotation speed ωi are in synchronization with each other andthe state that the clutch 20 is synchronized.

At the step S73, the control portion 40 outputs a control signal to theactuator 50 to have the clutch 20 to be completely in engagement state.Thus the output shaft EG-1 and the input shaft 51 are completelyconnected. Then the program goes to the step S74.

At the step S74, the control portion 40 starts execution of the secondengine start process. This second engine starting process will beexplained with reference to the flowchart shown in FIG. 9. When thesecond engine start process is started and when the control portion 40judges that the engine EG has started at the step S74-1 (S74-1; YES),the second engine start process ends (process of the step S74 in FIG. 4ends) and at the same time the engine start control in FIG. 4 ends. Whenthe control portion 40 judges that the engine EG has not started at thestep S74-1 (S74-1; NO), the program goes to the step S74-2.

At the step S74-2, when the control portion 40 judges that the enginerotation speed ωe is judged to be equal to or more than the aboveexplained engine starting rotation speed (S74-2; YES), the program goesto the step S74-3 and the engine rotation speed ωe is judged to be lessthan the engine starting rotation speed (S74-2; NO), the program goes tothe step S74-4.

At the step S74-3, the control portion 40 injects the fuel by the fuelinjection device and at the same time ignites the plugs to start theengine EG. After the process of the step S74-3 ends, the second enginestart process ends (the process of the step S74 in FIG. 4 ends) and atthe same time the engine start process in FIG. 4 ends.

At the step S74-4, the control portion 40 outputs a control signal tothe first inverter 31 to increase the rotation speed ωMG1 r of the firstmotor/generator MG1, thereby to increase the engine rotation speed ωe.After the process of the step S74-4, the program returns to the stepS74-2.

When the engine EG starts, the control portion 40 outputs the controlsignal to the engine EG to generate a desired engine rotation driveforce at the engine EG and at the same time outputs the control signalto the first inverter 31 to start electricity generation at the firstmotor/generator MG1. Under this state, the vehicle is driven under thesplit running mode.

Advantageous Effects of the Embodiment

As explained above, at the step S61-2 in FIG. 5, the control portion 40(allowable clutch heat generation amount calculating means) calculatesthe allowable clutch heat generation amount Qtmax and at the step S70 inFIGS. 4, 11 and 14, the control portion 40 (motor/generator rotationcontrol means) controls the rotation speed of the first motor/generatorMG1 so that the heat generation amount does not exceed the allowableclutch heat generation amount Qtmax. By this, the heat generation amountof the clutch 20 can be limited to the allowable clutch heat generationamount Qtmax or less. Thus, the overheating of the clutch 20 can beprevented from deterioration in life and the deterioration inperformance quality of the clutch 20.

Further, at the step S61-5 in FIG. 5, the control portion 40 (allowableclutch difference rotation speed calculating means) calculates theallowable clutch difference rotation speed Δ{tilde over (ω)} max whichis the difference in rotation speed between the output shaft EG-1 andthe input shaft 51 based on the allowable clutch heat generation amountQtmax. Then, at the step S70 in FIGS. 4, 11 and 14, the control portion40 (motor/generator rotation control means) controls the rotation speedof the first motor/generator MG1 so that the clutch difference rotationspeed Δ{tilde over (ω)} r which is the difference in rotation speedbetween the output shaft EG-1 and the input shaft 51 does not exceed theallowable clutch difference rotation speed Δ{tilde over (ω)} max. Bythis, the change of the clutch difference rotation speed of the clutch20 due to the vehicle speed change and the increase ratio of the enginerotation speed {tilde over (ω)} e can be prevented. Since the clutchdifference rotation speed Δ{tilde over (ω)} r is controlled not toexceed the allowable clutch heat generation amount Qtmax, the heatgeneration amount of the clutch 20 can be surely limited to theallowable clutch heat generation amount Qtmax or less.

At the step S61-5 in FIG. 5, the control portion 40 (allowable clutchdifference rotation speed calculating means) calculates the allowableclutch difference rotation speed Δ{tilde over (ω)} _(—)0max at the startof engagement and at the step S65 in FIG. 4, the control portion 40(motor/generator rotation control means) controls the rotation speed ofthe first motor/generator MG1 so that the clutch difference rotationspeed Δ{tilde over (ω)} _(—)0 at the start of engagement becomes equalto or less than the clutch difference rotation speed Δ{tilde over (ω)}_(—)0max at the start of engagement. Thus, before the clutch is engaged,the clutch 20 difference rotation speed is controlled to be equal to orless than the allowable clutch difference rotation speed Δ{tilde over(ω)} _(—)0max at the start of engagement which is calculated not toexceed the allowable clutch heat generation amount Qtmax. Accordingly,the heat generation amount of the clutch 20 can be surely prevented fromexceeding the allowable clutch heat generation amount Qtmax under theclutch 20 being in engagement.

Since the clutch 20 starts engagement at the rotation speed less thanthe allowable clutch difference rotation speed Δ{tilde over (ω)}_(—)0max at the start of engagement at which speed the clutch can startengagement, an engagement interruption due to an overheating of theclutch 20 during engagement can be prevented thereby to surely engagethe clutch 20.

Further, at the step S65 in FIG. 4, the control portion 40 controls therotation speed of the motor/generator MG1 so that the input shaftrotation speed {tilde over (ω)} i becomes the target input shaftrotation speed {tilde over (ω)} i_(—)0 at the start of engagement (whichis equal to the allowable clutch difference rotation speed Δ{tilde over(ω)} _(—)0max at the start of engagement). Further, at the step S70 inFIG. 4, the control portion 40 controls the rotation speed {tilde over(ω)} MG1 r of the first motor/generator MG1 to be the target input shaftrotation speed {tilde over (ω)} it under the clutch being in engagement.As stated, the clutch 20 is engaged keeping the high rotation speed ofthe input shaft 51 within a range that the clutch 20 does not overheat,the engine EG start is quickly performed preventing the clutch fromoverheating.

As shown in FIG. 7A, when the clutch difference rotation speed Δ{tildeover (ω)} r before the engagement starts is equal to or less than theallowable clutch difference rotation speed Δ{tilde over (ω)} _(—)0max atthe start of engagement (S62 in FIG. 4: YES), the clutch 20 is engaged,with keeping the current clutch difference rotation speed Δ{tilde over(ω)} r. Thus, after confirmation that the heat generation amount of theclutch 20 has not exceeded the allowable clutch heat generation amountQtmax, at the time the clutch 20 starts engagement, the clutch 20 isengaged without executing control of the clutch difference rotationspeed Δ{tilde over (ω)} r by the first motor/generator MG1, keeping thecurrent clutch difference rotation speed Δ{tilde over (ω)} r. Therefore,the engagement of the clutch 20 can be performed quickly and further theenergy consumption consumed by the execution of the control of theclutch difference rotation speed Δ{tilde over (ω)} r can be prevented.

Further at the step S69, the control portion 40 (target input shaftrotation speed calculating means) renews the target input shaft rotationspeed {tilde over (ω)} it during the engagement based on the targetinput shaft rotation speed {tilde over (ω)} it_(—)0 at the start ofengagement (which is equal to the allowable clutch difference rotationspeed Δ{tilde over (ω)} —0max at the start of engagement), enginerotation speed {tilde over (ω)} e and the target clutch synchronizingtime Tst. At the step S70, the control portion 40 (motor/generatorrotation control means) controls the rotation speed {tilde over (ω)} MG1r of the first motor/generator MG1 so that the rotation speed of theinput shaft 51 during the clutch being in engagement becomes the targetinput shaft rotation speed {tilde over (ω)} it during engagement.

According to the embodiment, the control portion 40 (target input shaftrotation speed calculating means), using the formula (5) describedabove, calculates the target input shaft rotation speed {tilde over (ω)}it during the clutch engagement, the clutch 20 can be surelysynchronized within the target clutch synchronizing time Tst andaccordingly, the heat generation amount of the clutch 20 can besuppressed to the allowable clutch heat generation amount Qtmax or lessto surely prevent overheating of the clutch 20. The advantages and thefunction thereof will be explained hereinafter in more detail.

The allowable clutch heat generation amount Qtmax is the valuecalculated by integrating a predetermined coefficient into the timeintegrated from the target clutch synchronizing time Tst of the targetclutch difference rotation speed Δ{tilde over (ω)} t. This isillustrated with an area (shaded area) enclosed by the vertical axis,horizontal axis and the allowable clutch difference rotation speedΔ{tilde over (ω)} max line in FIG. 7.

At the step S62, when the judgment is NO, as shown with the bold line inFIG. 7B, the target clutch difference rotation speed Δ{tilde over (ω)} tis set so that the target clutch difference rotation speed Δ{tilde over(ω)} t at the start of engagement of the clutch 20 becomes the allowableclutch difference rotation speed Δ{tilde over (ω)} _(—)0max at the startof engagement and the target clutch difference rotation speed Δ{tildeover (ω)} t during the engagement of the clutch 20 engagement graduallydecreases with time from the start of engagement of the clutch 20 andafter the target clutch synchronizing time Tst, becomes zero. In otherwords, as shown with the bold line in FIG. 7, the relationship betweenthe target clutch difference rotation speed Δ{tilde over (ω)} t and theelapsed time “t” elapsed from the start of the clutch 20 engagement is adirect function in which the target clutch difference rotation speedΔ{tilde over (ω)} t gradually decreases as the elapsed time “t”increases.

At the step S70 in FIG. 4, the control portion 40 (motor/generatorrotation control means) controls the rotation speed {tilde over (ω)} MG1r of the first motor/generator MG1 so that the rotation speed of theinput shaft 51 during clutch 20 being in engagement becomes the targetinput shaft rotation speed {tilde over (ω)} it. Therefore, even theengine EG rotation speed did not raise as intended according to theformula (4) above, or even the vehicle speed V is changed, as shown withthe fine line in FIG. 7, the clutch difference rotation speed Δ{tildeover (ω)} r gradually decreases with time from the start of engagementof the clutch 20 and becomes zero after the target clutch synchronizingtime Tst elapsed. In other words, as shown with the fine line in FIG. 7,the relationship between the clutch difference rotation speed Δ{tildeover (ω)} r and the elapsed time “t” elapsed from the start of theclutch 20 engagement is approximately a direct function in which theclutch difference rotation speed Δ{tilde over (ω)} r gradually decreasesas the elapsed time “t” increases. Thus, the heat amount generated atthe clutch 20 under engagement can be surely suppressed to the allowableclutch heat generation amount Qtmax (shaded area in FIG. 7).

On the other hand, as shown with the chain line, the heat generationamount at the time the clutch 20 is engaged exceeds the allowable clutchheat generation amount Qtmax (shaded area in FIG. 7), in case the clutchdifference rotation speed Δ{tilde over (ω)} r does not drop after acertain time elapsed from the start of engagement of the clutch.Further, as shown with the chain line 5 in FIG. 7B, the vehicle shockmay be generated due to a sudden drop of the clutch difference rotationspeed Δ{tilde over (ω)} r immediately after the start of engagement ofthe clutch 20. According to this embodiment, since the clutch differencerotation speed Δ{tilde over (ω)} r is controlled to agree with the fineline in FIG. 7, the heat generation amount of the clutch 20 at theengagement can be suppressed to the allowable clutch heat generationamount Qtmax and accordingly the generation of the vehicle shock can beprevented.

As shown with the bold broken line in FIG. 7, the relationship betweenthe allowable clutch difference rotation speed Δ{tilde over (ω)} max andthe elapsed time “t” from the start of engagement of the clutch 20 is adirect function in which the allowable clutch difference rotation speedΔ{tilde over (ω)} max gradually decreases as the elapsed time “t”increases. Accordingly, at the step S61-5, the allowable clutchdifference rotation speed Δ{tilde over (ω)} _(—)0max at the start ofengagement can be surely and easily calculated.

Further, at the step S61-2 in FIG. 5, the control portion 40 (allowableclutch heat generation amount calculating means) calculates theallowable clutch heat generation amount Qtmax based on the currentclutch temperature Tcrt (temperature of the friction member 22 a) andthe clutch allowable temperature Tmax which corresponds to thetemperature allowable for the clutch 20 (friction member 22 a). Thus,regardless of the current temperature of the clutch 20, the temperatureof the clutch 20 would not exceed the clutch allowable temperature Tmaxat the clutch engagement time. Accordingly, overheating of the clutch 20can be surely prevented. In other words, since the friction member 22 akeeps the temperature lower than the heat resistance temperature of thefriction member 22 a, overheating of the friction member 22 a can bealso prevented. Still further, since the allowable clutch heatgeneration amount Qtmax can be confirmed, the dropping amount of theinput shaft rotation speed {tilde over (ω)} i at the steps S64 throughS66 in FIG. 4 can be minimized, and the clutch 20 can quickly enter intothe engagement operation (S67 and S68 in FIG. 4). Further, a wastedenergy consumption derived from the extra driving operation of the firstmotor/generator MG1 can be prevented.

At the step S61-4 in FIG. 5, the control portion 40 (allowable clutchdifference rotation speed calculating means) calculates the relationshipbetween the clutch difference rotation speed Δ{tilde over (ω)} _(—)0 atthe start of engagement and the actual clutch heat generation amount Qrwhich relationship is a quadratic function as shown in FIG. 6, based onthe friction torque Te of the engine EG, engine inertia le and thetarget clutch synchronizing time Tst. At the step S61-5 in FIG. 5, thecontrol portion 40 calculates the allowable clutch difference rotationspeed Δ{tilde over (ω)} _(—)0max at the start of engagement (rotationspeed at the intersection point shown in FIG. 6) based on the allowableclutch heat generation amount Qtmax and the relationship between theclutch difference rotation speed Δ{tilde over (ω)} _(—)0 at the start ofengagement and the actual clutch heat generation amount Qr.

As explained, since the allowable clutch difference rotation speedΔ{tilde over (ω)} _(—)0max at the start of engagement is calculated andthe allowable clutch difference rotation speed Δ{tilde over (ω)} max isset considering the values of the engine friction torque, engine inertiale and the target clutch synchronizing time Tst, the heat generationamount of the clutch 20 (friction member 22 a) can be surely limited tothe allowable clutch heat generation amount Qtmax regardless of thevalues of the values of the engine friction torque, the engine inertiale and the target clutch synchronizing time Tst. Further, preventing theclutch 20 from overheating, the clutch 20 can be engaged within thetarget clutch synchronizing time Tst to complete the clutch engagementquickly.

Further, interruption of engagement operation of the clutch 20 due tooverheating during the engagement performance of the clutch 20 can beprevented. Further, if the temperature of the clutch 20 has alreadyreached to the allowable temperature, the allowable clutch differencerotation speed Δ{tilde over (ω)} _(—)0max at the start of engagement iscalculated and the first motor/generator MG1 is controlled so that theclutch difference rotation speed Δ{tilde over (ω)} becomes zero and theclutch 20 is engaged. Under the above control situation, without anyfurther control processing, the above control is executed automatically.

At the step S67 in FIG. 4, the control portion 40 (target clutchtransmitting torque calculating means) calculates the target clutchtransmitting torque Tct by substituting the target input shaft rotationspeed {tilde over (ω)} it_(—)0 at the start of engagement, engine EGfriction torque Te, engine inertia le and the target clutchsynchronizing time Tst into the above formula (3). Then at the step S68in FIG. 4, the control portion 40 (clutch control means) controls theclutch 20 so that the clutch transmitting torque during engagement ofthe clutch 20 becomes the target clutch transmitting torque Tct. Thus,the clutch transmitting torque is stable and constant when the clutch 20is engaged. It is noted that the heat generation amount of the clutch 20depends on the transmitting torque and as stated above, since the clutch20 transmitting torque is constant at the engagement of the clutch 20,the clutch heat generation amount can be suppressed to the allowableclutch heat generation amount Qtmax which is set in advance byestimation.

Second Embodiment

The hybrid drive device according to the second embodiment will beexplained hereinafter with reference to FIGS. 10 through 12, explainingthe different points from those in the first embodiment. According tothe second embodiment, as shown in FIG. 10, the control portion 40variably controls the target clutch synchronizing time Tst so that theheat generation amount during the clutch 20 being in engagement becomesequal to or less than the allowable clutch heat generation amount Qtmax.

The engine start control according to the second embodiment will beexplained hereinafter with reference to the flowchart of FIG. 11. Whenthe engine start control according to the second embodiment begins, atthe step S81, the control portion 40 calculates the allowable clutchsynchronizing time Tstmax. More specifically, the allowable clutch heatgeneration amount Qtmax is calculated according to the same manner asexplained in the step S61-1 and the step S61-2 in FIG. 5. Similarly thecontrol portion 40 calculates the engine EG friction torque Te by thesame way as explained in the step S61-3 in FIG. 5 above.

Then the control portion 40 calculates the relationship between theclutch synchronizing time Tst and the actual clutch heat generationamount Qr (See FIG. 12) inputting the engine EG friction torque Te,clutch difference rotation speed Δ{tilde over (ω)} _(—)0 at the start ofengagement, engine inertia le into the mapping data or the calculatingformula which illustrates the relationship thereof with the frictiontorque Te of the engine EG, clutch difference rotation speed Δ{tildeover (ω)} _(—)0 at the start of engagement, engine inertia le, actualclutch heat generation amount Qr and the clutch synchronizing time Tst.It is noted that since the engine EG is stopped at the start of theclutch 20 engagement, the value of the clutch difference rotation speedΔ{tilde over (ω)} _(—)0 at the start of engagement is the value of theinput shaft rotation speed {tilde over (ω)} i _(—)0 at the start ofengagement of the clutch 20. The control portion 40 inputs the currentinput shaft rotation speed {tilde over (ω)} i as the clutch differencerotation speed Δ{tilde over (ω)} _(—)0 at the start of engagement intothe mapping data or the calculation formula. It is noted that when theclutch difference rotation speed Δ{tilde over (ω)} is set according tothe formula (11) above, the relationship between the clutchsynchronizing time Tst and the actual clutch heat generation amount Qrbecomes the direct function as shown in FIG. 12.

It is noted that the mapping data or the calculation formula is set tobe a direct function in which the actual heat generation amount Qrbecomes large as the friction torque Te becomes large in therelationship with the clutch synchronizing time Tst (the direct functionbecomes more in the direct function f1 side than in the direct functionf3 side). Further, the mapping data or the calculation formula is set tobe a direct function in which the actual heat generation amount Qrbecomes large as the clutch difference rotation speed Δ{tilde over (ω)}_(—)0 at the start of engagement becomes large with respect to therelationship with the clutch synchronizing time Tst (the direct functionbecomes more in the direct function f1 side than in the direct functionf3 side). Still further, assuming that the clutch synchronizing time Tstis set to be the x-axis and the actual clutch heat generation amount Qris set to be the y-axis, the y-segment of the direct function becomeslarge as the engine inertia le becomes large according to the mappingdata or the calculation formula. Further, in the mapping data or thecalculation formula, when the clutch difference rotation speed Δ{tildeover (ω)} _(—)0 at the start of engagement becomes large as they-segment of the direct function becomes large.

The control portion 40 calculates the allowable clutch synchronizingtime Tstmax based on the allowable clutch heat generation amount Qtmaxcalculated above and the relationship between the clutch synchronizingtime Tst calculated above and the actual clutch heat generation amountQr, which is represented by a direct function. More specifically, asshown in FIG. 12, the allowable clutch synchronizing time Tstmax iscalculated from the intersection point between the allowable clutch heatgeneration amount Qtmax which is represented as a direct function andthe relationship between clutch synchronizing time Tst and the actualclutch heat generation amount Qr which is represented as a directfunction. After the processing of step S81, the program goes to the stepS82.

At the step S81, the control portion 40 calculates the allowable clutchdifference rotation speed Δ{tilde over (ω)} max by substituting theclutch difference rotation speed Δ{tilde over (ω)} _(—)0 at the start ofengagement, calculated allowable clutch synchronizing time Tstmax andthe elapsed time “t” elapsed from the start of engagement of the clutch20 into the following formula (14). (Bold broken line in FIG. 10).

Δ{tilde over (ω)} max=−(Δ{tilde over (ω)} _(—)0Tstmax)×t+Δ{tilde over(ω)} _(—)0   (14)

-   Δ{tilde over (ω)} max: allowable clutch difference rotation speed-   Δ{tilde over (ω)} _(—)0: clutch difference rotation speed at the    start of engagement-   Tstmax: allowable clutch synchronizing time-   “t”: elapsed time from the start of engagement of the clutch 20.

At the step S82, when the control portion 40 judged that a definedclutch synchronizing time Tststd is equal to or less than the allowableclutch synchronizing time Tstmax (S82: YES), advances the program to thestep S83. When the control portion 40 judged that the defined clutchsynchronizing time Tststd is longer than the allowable clutchsynchronizing time Tstmax (S82: NO), advances the program to the stepS84. It is noted that the defined clutch synchronizing time Tststd isthe synchronizing time of the clutch 20 predetermined in advance.

At the step S83, the control portion 40 sets the defined clutchsynchronizing time Tststd to be the target clutch synchronizing time Tstand advances the program to the step S67.

At the step S84, the control portion 40 sets the allowable clutchsynchronizing time Tstmax to the target clutch synchronizing time Tstand advances the program to the step S67.

The processing of the engine start control according to the secondembodiment in the steps S67 through S74 is the same as that of theengine start control according to the first embodiment in the steps S67through S74 and therefore the explanation thereof will be omitted.

It is noted that at the step S67, the control portion 40 calculates thetarget clutch transmitting torque Tct by substituting the currentrotation speed of the input shaft 51 as the target input shaft rotationspeed {tilde over (ω)} it_(—)0 at the start of engagement into the aboveformula (3).

It is noted that when the judgment at the step S82 is “YES”, at the stepS69, the control portion 40 renews the target input shaft rotation speed{tilde over (ω)} it during the clutch 20 being in engagement bysubstituting the defined clutch synchronizing time Tststd as the targetclutch synchronizing time Tst into the formula (5) above. Thus, when thetarget input shaft rotation speed {tilde over (ω)} it is renewed, asshown in FIG. 10A with the bold line, the relationship between thetarget clutch difference rotation speed Δ{tilde over (ω)} t and theelapsed time “t” from the start of engagement of the clutch 20 isrepresented as a direct function in which the target clutch differencerotation speed Δ{tilde over (ω)} t gradually decreases as the elapsedtime “t” increases and becomes zero after the defined clutchsynchronizing time Tststd which corresponds to the target clutchsynchronizing time Tst elapsed. The difference rotation speed Δ{tildeover (ω)} r of the clutch 20 drops along the line of target clutchdifference rotation speed Δ{tilde over (ω)} t by controlling therotation speed of the first motor/generator MG1 at the step S70.Accordingly, the difference rotation speed Δ{tilde over (ω)} of theclutch 20 gradually drops with time from the start of engagement of theclutch 20 along the line of the target clutch difference rotation speedΔ{tilde over (ω)} t as shown in FIG. 10A with the fine line andeventually becomes zero after the target clutch synchronizing time Tstelapsed and the clutch 20 is synchronized.

Further, when the judgment at the step S82 is “NO”, at the step S69, thecontrol portion 40 renews the target input shaft rotation speed {tildeover (ω)} it during the clutch 20 being in engagement by substitutingthe allowable clutch synchronizing time Tstmax as the target clutchsynchronizing time Tst into the formula (5) above. Thus, as shown inFIG. 10B with the bold line, the relationship between the target clutchdifference rotation speed Δ{tilde over (ω)} t and the elapsed time “t”from the start of engagement of the clutch 20 is represented as a directfunction in which the target clutch difference rotation speed Δ{tildeover (ω)} t gradually decreases as the elapsed time “t” increases andbecomes zero after the allowable clutch synchronizing time Tstmax whichcorresponds to the target clutch synchronizing time Tst elapsed. It isnoted here that the judgment at the step S82 is “NO”, the target clutchdifference rotation speed Δ{tilde over (ω)} t is the same with theallowable clutch difference rotation speed Δ{tilde over (ω)} max (Boldbroken line). Accordingly, the difference rotation speed Δ{tilde over(ω)} of the clutch 20 gradually drops with time from the start ofengagement of the clutch 20 along the line of the target clutchdifference rotation speed Δ{tilde over (ω)} t as shown in FIG. 10B withthe fine line and eventually becomes zero after the target clutchsynchronizing time Tst elapsed and the clutch 20 is synchronized.

As shown at the step S81 in FIG. 11, the control portion 40 (allowableclutch synchronizing time calculating means) calculates the allowableclutch synchronizing time Tstmax which corresponds to the clutchsynchronizing time allowable for clutch engagement based on theallowable clutch heat generation amount Qtmax. Then, as shown in FIG.10, the control portion 40 (motor/generator rotation control means) inthe steps S68 through S72 in FIG. 11 controls the rotation speed of thefirst motor/generator MG1 so that the clutch difference rotation speedΔ{tilde over (ω)} r gradually decreases with time from the start ofengagement of the clutch 10 and finally becomes zero within theallowable clutch synchronizing time Tstmax. Accordingly, since theclutch synchronizing time before the clutch 20 being engaged is set tobe less than the allowable clutch synchronizing time Tstmax calculatednot to exceed the allowable clutch heat generation amount Qtmax (shadedarea shown in FIG. 10), the heat generation amount under the clutch 20being in engagement can be surely prevented from exceeding the allowableclutch heat generation amount and overheating of the clutch 20 can besurely prevented.

It is noted that according to the hybrid drive device according to thesecond embodiment, after the process of the step S74 in FIG. 11 ends andafter the clutch has been engaged, if the allowable clutch heatgeneration amount Qmax is smaller than a first defined heat generationamount, the control portion 40 keeps the engagement state of the clutch20 and forbids the disconnection of the clutch 20 not to perform clutchengagement until the allowable clutch heat generation amount Qmaxreaches to a second defined heat generation amount (which is equal to ormore than the first defined heat generation amount value). Thus, theoverheating of the clutch 20 can be prevented.

Third Embodiment

The third embodiment of the hybrid drive device will be explainedhereinafter with reference to FIGS. 13 through 15, but only thedifferent points from the first embodiment. According to the thirdembodiment, as shown in FIG. 13, the control portion 40 varies thecurvature of the function (curved line) which represents therelationship between the target clutch difference rotation speed Δ{tildeover (ω)} t and the elapsed time from the start of engagement of theclutch 20 so that the heat generation amount during the clutch 20 beingin engagement can be set to equal to or less than the allowable clutchheat generation amount Qtmax.

The engine start control according to the third embodiment will beexplained with reference to the flowchart in FIG. 14. When the enginestart control according to the third embodiment starts, at the step S91,the control portion 40 calculates the allowable curvature of the curvedline (hereinafter referred to simply as “allowable curvature” from timeto time) representing the relationship between the target clutchdifference rotation speed Δ{tilde over (ω)} t and the elapsed time fromthe start of engagement of the clutch 20. More specifically, the controlportion 40 calculates the allowable clutch heat generation amount Qtmax,with the same way as in the steps S61-1 and S61-2 in FIG. 5 explainedabove. Then the control portion 40 calculates the engine EG frictiontorque Te with the same way as in the steps S61-3 in FIG. 5.

Then, the control portion 40 calculates a function (curved line) asshown in FIG. 15, which represents the relationship between thecurvature of the curved line representing the relationship between theclutch difference rotation speed Δ{tilde over (ω)} and the elapsed time“t” from the start of engagement of the clutch 20 (hereinafter referredto as “curvature of clutch difference rotation speed Δ{tilde over (ω)}”) and the actual clutch heat generation amount Qr by inputting theengine EG friction torque Te, clutch difference rotation speed Δ{tildeover (ω)} _(—)0 at the start of engagement, engine inertia le and thetarget clutch synchronizing time Tst into the mapping data or thecalculating formula which illustrates the relationship thereof with thefriction torque Te of the engine EG, clutch difference rotation speedΔ{tilde over (ω)} _(—)0 at the start of engagement, engine inertia le,actual clutch heat generation amount Qr, the clutch synchronizing timeTst and the relationship between the curvature of the curved linerepresenting the relationship between the clutch difference rotationspeed Δ{tilde over (ω)} and the elapsed time “t” from the start ofengagement of the clutch 20. It is noted that since the engine EG isstopped at the start of the clutch 20 engagement, the value of theclutch difference rotation speed Δ{tilde over (ω)} _(—)0 at the start ofengagement is the value of the input shaft rotation speed {tilde over(ω)} i_(—)0 at the start of engagement of the clutch 20. The controlportion 40 inputs the current input shaft rotation speed {tilde over(ω)} i as the clutch difference rotation speed Δ{tilde over (ω)} _(—)0at the start of engagement into the mapping data or the calculationformula.

It is noted that the mapping data or the calculation formula is set tocalculate a function in which the actual heat generation amount Qrbecomes large as the friction torque Te becomes large with respect tothe relationship with the curvature of the clutch difference rotationspeed Δ{tilde over (ω)} (the function becomes more in the function f1side than in the function f3 side). Further, the mapping data or thecalculation formula is set to calculate a function in which the actualheat generation amount Qr becomes large as the clutch differencerotation speed Δ{tilde over (ω)} _(—)0 at the start of engagementbecomes large with respect to the relationship with the curvature of theclutch difference rotation speed Δ{tilde over (ω)} (the function becomesmore in the function f1 side than in the function f3 side). Stillfurther, the mapping data or the calculation formula is set to calculatea function in which the actual heat generation amount Qr becomes largeas the engine inertia le becomes large with respect to the relationshipwith the curvature of the clutch difference rotation speed Δ{tilde over(ω)} (the function becomes more in the function f1 side than in thefunction f3 side). The mapping data or the calculation formula isfurther set to calculate a function in which the actual heat generationamount Qr becomes large as the target clutch synchronizing time Tstbecomes large with respect to the relationship with the curvature of theclutch difference rotation speed Δ{tilde over (ω)} (the function becomesmore in the function 11 side than in the function f3 side).

Next, the control portion 40 calculates the allowable curvature of thecurved line (hereinafter referred to as simply “allowable curvature”)which represents the relationship between the target clutch differencerotation speed Δ{tilde over (ω)} t and the elapsed time from the startof engagement of the clutch 20 based on the allowable clutch heatgeneration amount Qtmax and the function representing the relationshipbetween the target clutch difference rotation speed Δ{tilde over (ω)} tcurvature and the actual heat generation amount Qr. In more detail, asshown in FIG. 15, the curvature of the target clutch difference rotationspeed Δ{tilde over (ω)} t is calculated from the intersection pointbetween the allowable clutch heat generation amount Qtmax which isrepresented as the direct function and the relationship between thecurvature of the target clutch difference rotation speed Δ{tilde over(ω)} t and the actual clutch heat generation amount Qr which isrepresented as a function. After the process of the step S91, theprogram goes to the step S92.

At the step S92, when the control portion 40 judged that the allowablecurvature calculated at the step S91 is equal to or less than a standardcurvature of the curved line (hereinafter referred to simply as“standard curvature”) which represents the relationship between thetarget clutch difference rotation speed Δ{tilde over (ω)} t and theelapsed time from the start of engagement of the clutch 20 (S92: YES),the control portion 40 advances the program to the step S93 and when thecontrol portion 40 judged that allowable curvature calculated at thestep S91 is larger than the standard curvature (S92: NO), the controlportion 40 advances the program to the step S94. It is noted here thatthe standard curvature is set in advance and for example, as shown inFIG. 13A, the curvature may be set to be zero and the relationshipbetween the target clutch difference rotation speed Δ{tilde over (ω)} tand the elapsed time from the start of engagement of the clutch 20 isrepresented as a direct function.

At the step S93, the control portion 40 sets the “standard curvature” tobe the “target curvature” of the target clutch difference rotation speedΔ{tilde over (ω)} t (hereinafter referred to as simply “targetcurvature”) and advances the program to the step S95.

At the step S94, the control portion 40 sets the “allowable curvature”to be the “target curvature” and advances the program to the step S95.

At the step S94, the control portion 40 calculates the target clutchtransmitting torque Tct based on the target curvature. Morespecifically, the control portion 40 calculates the target clutchtransmitting torque Tct by inputting the target curvature, engine EGfriction torque Te, clutch difference rotation speed Δ{tilde over (ω)}_(—)0 at the start of engagement, engine inertia le and target clutchsynchronizing time Tst into the mapping data or the calculation formulawhich illustrates the relationship thereof with the target curvature,engine EG friction torque Te, clutch difference rotation speed Δ{tildeover (ω)} _(—)0 at the start of engagement, engine inertia le and targetclutch synchronizing time Tst and the target clutch transmitting torqueTct. After the process at the step S95, the program goes to the stepS68.

The processing of the engine start control according to the thirdembodiment in the steps S68 through S71 is the same as that of theengine start control according to the first embodiment in the steps S68through S71 and therefore the explanation thereof will be omitted.

At the step S97, when the control portion 40 judged that the enginerotation speed {tilde over (ω)} e agrees to the input shaft rotationspeed {tilde over (ω)} i (S97: YES), the program goes to the step S73and when the control portion 40 judged that the engine rotation speed{tilde over (ω)} e does not agree to the input shaft rotation speed{tilde over (ω)} i (S97: NO), the program returns to the step S95.

The processing of the engine start control according to the thirdembodiment in the steps S73 and S74 is the same as that of the enginestart control according to the first embodiment in the steps S73 and S74and therefore the explanation thereof will be omitted.

It is noted that when the judgment at the step S92 is “YES”, at the stepS93, the control portion 40 sets the standard curvature to the targetcurvature. Then, as shown in FIG. 13A with bold line, the curvaturerepresenting the relationship between the target clutch differencerotation speed Δ{tilde over (ω)} t and the elapsed time “t” from thestart of engagement of the clutch 20 becomes the standard curvaturewhich is a function, in which the target clutch difference rotationspeed Δ{tilde over (ω)} t gradually decreases as the elapsed time “t”increases and becomes zero after the target clutch synchronizing timeTst elapsed. The difference rotation speed {tilde over (ω)} r of theclutch 20 drops along the line of the clutch difference rotation speedΔ{tilde over (ω)} by controlling the rotation speed of the firstmotor/generator MG1 at the step S70. Accordingly, the differencerotation speed Δ{tilde over (ω)} r of the clutch 20 gradually drops withtime from the start of engagement of the clutch 20 along the line of thetarget clutch difference rotation speed Δ{tilde over (ω)} t as shown inFIG. 13A with the fine line and eventually becomes zero after the targetclutch synchronizing time Tst elapsed and the clutch 20 is synchronized.

Further, when the judgment at the step S92 is “NO”, at the step S94, thecontrol portion 40 sets the standard curvature to the target curvature.Then, as shown in FIG. 13B with the bold line, the curvature of thecurved line representing the relationship between the target clutchdifference rotation speed Δ{tilde over (ω)} t and the elapsed time “t”from the start of engagement of the clutch 20 is represented as afunction in which the target clutch difference rotation speed Δ{tildeover (ω)} t gradually decreases as the elapsed time “t” increases andbecomes zero after the target clutch synchronizing time Tst elapsed. Itis noted here as shown in FIG. 13B, the target clutch differencerotation speed Δ{tilde over (ω)} t is the same value with the allowableclutch difference rotation speed Δ{tilde over (ω)} max (See bold brokenline in FIG. 13B). Therefore, as shown in FIG. 13B with the fine line,the clutch difference rotation speed Δ{tilde over (ω)} r gradually dropswith time from the start of engagement of the clutch 20 along the lineof the target clutch difference rotation speed Δ{tilde over (ω)} t andeventually becomes zero after the target clutch synchronizing time Tstelapsed and the clutch 20 is synchronized.

As explained, the hybrid drive device according to the third embodimentalso suppresses the heat generation amount of the clutch 20 to theallowable clutch heat generation amount Qtmax (shaded area in FIG. 13)or less and the overheating of the clutch 20 can be surely prevented.

It is noted that according to the hybrid drive device according to thethird embodiment, after the process of the step S74 in FIG. 14 ends andafter the clutch has been engaged, if the allowable clutch heatgeneration amount Qmax is smaller than a first defined heat generationamount, the control portion 40 keeps the engagement state of the clutch20 and forbids the disconnection of the clutch 20 not to perform clutchengagement until the allowable clutch heat generation amount Qmaxreaches to a second defined heat generation amount (which is equal to ormore than the first defined heat generation amount value). Thus, theoverheating of the clutch 20 can be prevented.

In this embodiment, the control portion 40 varies the curvature of thefunction (curved line) which represents the relationship between thetarget clutch difference rotation speed Δ{tilde over (ω)} t and theelapsed time from, the start of engagement of the clutch 20. However,the control portion 40 is structured to vary a degree in the “n”-thdimension function representing the relationship between the targetclutch difference rotation speed Δ{tilde over (ω)} t and the elapsedtime from the start of engagement of the clutch 20. This may alsominimize the heat generation amount during the clutch 20 being inengagement to the allowable clutch heat generation amount Qtmax or less.

Fourth Embodiment

The fourth embodiment of the hybrid drive device 200 will be explainedwith reference to FIG. 16, explaining the different points from those ofthe hybrid drive device 100 in the first embodiment. The same structureof the hybrid drive device of this embodiment with the structure of thehybrid drive device 100 of the first embodiment will be referred to bythe same reference numerals or symbols and the explanation thereof willbe omitted.

The hybrid drive device 200 according to the fourth embodiment includesthe first rotor Ro1 of the first motor/generator MG1 connected to theinput shaft 51 and at the same time connected to the ring gear 14 of theplanetary gear mechanism 10. The sun gear 11 of the planetary gearmechanism 10 is connected to the second rotor Ro2 of the secondmotor/generator MG2. The carrier 13 is formed with an output gear 13 awhich is engaged with the input gear 72.

The ring gear 14 is rotatably connected to or securely fixed to ahousing 201 by means of a brake B. The brake B is controlled by thecontrol portion 40.

Under the electric running mode, the control portion 40 controls theactuator 50 to disconnect the clutch 20 and at the same time controlsthe brake B to fix the ring gear 14 to the housing 201. Further, thecontrol portion 40 outputs a control signal to the second inverter 32 torotationally drive the second motor/generator MG2 so that the rotationdrive force thereof agrees with the required drive force. Further, whena sufficient required drive force cannot be obtained only by therotation drive force from the second motor/generator MG2, the controlportion 40 controls the actuator 50 to disconnect the clutch 20 and atthe same time controls the brake B so that the ring gear 14 is rotatablyconnected to the housing 201. Then the control portion 40 outputscontrol signals to both first and second inverters 31 and 32 to driveboth first and second motor/generators MG1 and MG2 to output the driveforce to agree to the required drive force.

Under the split running mode, the control portion 40 controls theactuator 50 to engage the clutch 20 and at the same time controls thebrake B to rotatably support the ring gear 14 on the housing 201.Further, the control portion 40 outputs a control signal to the secondinverter 32 to drive the second motor/generator MG2 and at the same timecontrols the engine EG to generate a predetermined rotation drive force.Thus, the engine EG and the input shaft 51 are connected and the enginerotation drive force is transmitted to the first motor/generator MG1 andaccordingly to the ring gear 14. The first motor/generator MG1 generatesthe electricity by the engine rotation drive force. The engine rotationdrive force inputted to the ring gear 14 and the motor/generator MG2rotation drive force are transmitted to the drive wheels Wr and Wl.

According to this fourth embodiment, the following formula (7) isapplied instead of the formula (2) above.

{tilde over (ω)} MG1t=with   (7)

-   {tilde over (ω)} MG1 t: target rotation speed of the first    motor/generator MG1-   {tilde over (ω)} it: target input shaft rotation speed.

The control portion 40 executes the clutch/engine control (See FIG. 3)and the engine start control (See FIG. 4). It is noted however that inthe step S70 in FIG. 4, the control portion 40 rotatably controls therotation of the first motor/generator MG1 by outputting the controlsignal to the first inverter 31 so that the input shaft rotation speed{tilde over (ω)} i becomes equal to the target input shaft rotationspeed {tilde over (ω)} it_(—)0 at the start of engagement (equal to orless than the allowable clutch difference rotation speed Δ{tilde over(ω)} _(—)0max at the start of engagement). Further, in the step S70 inFIG. 4, the control portion 40, by outputting the control signal to thefirst inverter 31, rotatably controls the rotation of the firstmotor/generator MG1 so that the input shaft rotation speed {tilde over(ω)} i becomes equal to the target input shaft rotation speed {tildeover (ω)} it being in engagement.

It may be possible to implement an embodiment which combines thestructure of the hybrid drive device 200 according to the fourthembodiment with the engine start control of the second embodiment or thethird embodiment.

Fifth Embodiment

The hybrid drive device according to the fifth embodiment will beexplained, explaining the different points from those of the hybriddrive device 100 in the first embodiment. According to the firstembodiment, the control portion 40 controls the input shaft rotationspeed {tilde over (ω)} i by controlling the rotation speed of the firstmotor/generator MG1 when the clutch is engaged. However, according tothe fifth embodiment, the control portion 40 controls the clutchdifference rotation speed Δ{tilde over (ω)} r by controlling therotation speed of the first motor/generator MG1 when the clutch isengaged.

At the step S63, the control portion 40 sets the current clutchdifference rotation speed Δ{tilde over (ω)} r to the target clutchdifference rotation speed Δ{tilde over (ω)} t_(—)0 at the start ofengagement.

At the step S69, the control portion 40 calculates the target clutchdifference rotation speed Δ{tilde over (ω)} t by substituting the targetclutch difference rotation speed Δ{tilde over (ω)} t_(—)0 at the startof engagement, target clutch synchronizing time Tst and the elapsed time“t” from the start of engagement of the clutch 20 into the followingformula (13).

Δωt=−(Δωt _(—)0 Tst) ×t+Δωt _(—)0   (13)

-   Δωt : target clutch difference rotation speed:-   ωt_(—)0:target clutch difference rotation speed at the start of    engagement-   Tst: target clutch synchronizing time:-   t: elapsed time from the start of engagement of the clutch 20:

At the step S64, the control portion 40 sets the allowable clutchdifference rotation speed Δωt_(—)0max at the start of engagement of theclutch 20 to the target clutch difference rotation speed

-   Δωt_(—)0 at the start of engagement.

At the step S65, the control portion 40 controls the clutch differencerotation speed Δ{tilde over (ω)} r by controlling the rotation speed ofthe first motor/generator MG1 so that the clutch difference rotationspeed Δ{tilde over (ω)} r becomes the target clutch difference rotationspeed Δ{tilde over (ω)} t_(—)0 at the start of engagement calculated atthe step S64. This control is executed by PID (feedback control) whichis illustrated in FIG. 17 by the PID control block diagram. According tothe embodiment, as shown in FIG. 17, the PID controller 301 and thedisturbance observer 302 are incorporated into the control portion 40.However, these are structured separately from the control portion 40.The plant P which is the object of the control indicates the firstinverter 31 and the first motor/generator MG1 and the target amount isthe target clutch difference rotation speed Δ{tilde over (ω)} t and thecontrol amount is the clutch difference rotation speed Δ{tilde over (ω)}r.

The control portion 40 compares the target clutch difference rotationspeed Δ{tilde over (ω)} t and the clutch difference rotation speedΔ{tilde over (ω)} r and calculates the difference therebetween, thecontrol deviation “d”. Based on the control deviation “d”, a properamount of the operation amount “c” for adjusting the clutch differencerotation speed which corresponds to the control amount is calculated andthe calculated operation amount “c” is outputted to the first inverter31. The disturbance observer 302 calculates the disturbance amount whichis the variations of the change of the engine rotation speed {tilde over(ω)} e and change of the vehicle speed V based on the variation of theclutch difference rotation speed Δ{tilde over (ω)} r which correspondsto the control amount and executes a feedback control in which theoperation amount “c” is increased or decreased in the direction negatingthe influence of the disturbance on the control amount. The firstinverter 31 in which the operation amount c is inputted, then outputs ACcurrent to the first motor/generator MG1 in response to the newoperation amount “c”. The first motor/generator MG1 changes the clutchdifference rotation speed Δ{tilde over (ω)} r which corresponds to thecontrol amount.

According to the fifth embodiment, at the step S69 in FIG. 4, thecontrol portion 40 (target clutch difference rotation speed calculatingmeans) calculates the target clutch difference rotation speed Aunt bythe formula (13) above based on the allowable target clutch differencerotation speed Δ{tilde over (ω)} _(—)0max at the start of engagement andthe target clutch synchronizing time Tst. At the step S70 in FIG. 4, thecontrol portion 40 (motor/generator rotation control means) controls therotation speed of the first motor/generator MG1 so that the clutchdifference rotation speed Δ{tilde over (ω)} r during the clutch 20 beingin engagement becomes the target clutch difference rotation speedΔ{tilde over (ω)} t. Thus, the target clutch difference rotation speedΔ{tilde over (ω)} t which satisfies the allowable clutch differencerotation from the time the clutch 20 starts engagement until the clutch20 synchronizes after the target clutch synchronizing time elapsed.Therefore, the clutch 20 can be surely synchronized within the targetclutch synchronizing time Tst. The heat generation amount of the clutch20 in engagement can be suppressed to the allowable clutch heatgeneration amount Qtmax or less to surely prevent the overheating of theclutch 20.

Further, the control portion 40 (target clutch difference rotation speedcalculating means) calculates the target clutch difference rotationspeed Δ{tilde over (ω)} t so that the target clutch difference rotationspeed Δ{tilde over (ω)} t gradually decreases with time from the startof engagement of the clutch 20 and becomes zero after the target clutchsynchronizing time elapsed by using the formula (13) above (See FIG. 7).Then the control portion 40 (motor/generator rotation control means)controls the rotation speed of the first motor/generator MG1 so that theclutch difference rotation speed Δ{tilde over (ω)} r under the clutch 20being in engagement becomes the target clutch difference rotation speedΔ{tilde over (ω)} t. Accordingly, since the clutch difference rotationspeed Δ{tilde over (ω)} t is controlled to be gradually decreased withtime from the start of engagement of the clutch 20, the heat generationamount of the clutch 20 at the engagement can be suppressed to theallowable clutch heat generation amount Qtmax and at the same timegeneration of vehicle shock can be prevented.

(Sixth Embodiment)

The hybrid drive device according to the sixth embodiment will beexplained explaining the different points from the second embodiment.According to the second embodiment, the control portion 40 bycontrolling the rotation speed of the first motor/generator MG1 when theclutch is engaged, controls the input shaft rotation speed {tilde over(ω)} i. However, according to the sixth embodiment, the control portion40 by controlling the rotation speed of the first motor/generator MG1when the clutch is engaged controls the clutch difference rotation speed{tilde over (ω)} r.

At the step S82, when the judgment is YES, in the processing at the stepS69, the control portion 40 substitutes the defined clutch synchronizingtime Tststd as the target clutch synchronizing time Tst into the formula(15) bellow and at the same time substitutes the clutch differencerotation speed Δ{tilde over (ω)} _(—)0 at the start of engagement andthe elapsed time “t” from the start of engagement of the clutch 20 intothe formula (15) bellow to calculate and renew the target clutchdifference rotation speed Δ{tilde over (ω)} t.

Δωt=−(Δωit _(—)0/Tst)×t+ωe+Δω _(—)0   (15)

-   Δωt : target clutch difference rotation speed:-   Δω_(—)0: target clutch difference rotation speed at the start of    engagement-   Tst: target clutch synchronizing time:

At the step S70, the control portion 40 controls the clutch differencerotation speed Δ{tilde over (ω)} r by controlling the rotation speed ofthe motor/generator MG1 so that the clutch difference rotation speedΔ{tilde over (ω)} r becomes the target clutch difference rotation speedΔ{tilde over (ω)} t calculated at the step S69. The control executionstructure is the same with that explained with FIG. 17.

As explained, at the step S69, the target clutch difference rotationspeed Δ{tilde over (ω)} t is renewed, as shown in FIG. 10A with the boldline, the relationship between the target clutch difference rotationspeed Δ{tilde over (ω)} t and the elapsed time “t” from the start ofengagement of the clutch 20 is represented as a direct function in whichthe target clutch difference rotation speed Δ{tilde over (ω)} tgradually decreases as the elapsed time “t” increases and becomes zeroafter the defined clutch synchronizing time Tststd which corresponds tothe target clutch synchronizing time Tst elapsed. At the step S70, bycontrolling the rotation speed of the first motor/generator MG1, thedifference rotation speed Δ{tilde over (ω)} r of the clutch 20 dropsalong the line of the target clutch difference rotation speed Δ{tildeover (ω)} t. Therefore, the difference rotation speed Δ{tilde over (ω)}of the clutch 20 gradually decreases with time from the start ofengagement of the clutch 20 along the line of target clutch differencerotation speed Δ{tilde over (ω)} t as shown in FIG. 10A with the fineline, and after the target clutch synchronizing time Tst elapsed,becomes zero and the clutch 20 is synchronized.

When the judgment at the step S82 is “NO”, at the step S69, the controlportion 40 sets the allowable clutch synchronizing time Tstmax to be thetarget clutch synchronizing time Tst and substitutes the value into theformula (15) above. At the same time the control portion 40 substitutesthe clutch difference rotation speed Δ{tilde over (ω)} _(—)0 at thestart of engagement and the elapsed time “t” from the start ofengagement of the clutch 20 into the formula (15) above to calculate andrenew the target clutch difference rotation speed Δ{tilde over (ω)} t.

At the step S70, the control portion 40 controls the clutch differencerotation speed Δ{tilde over (ω)} r by controlling the rotation speed ofthe motor/generator MG1 so that the clutch difference rotation speedΔ{tilde over (ω)} r becomes the target clutch difference rotation speedΔ{tilde over (ω)} t calculated at the step S69. The control executionstructure is the same with that explained with FIG. 17.

Thus, when the target clutch difference rotation speed Δ{tilde over (ω)}t is renewed, as shown in FIG. 10B with the bold line, the relationshipbetween the target clutch difference rotation speed Δ{tilde over (ω)} tand the elapsed time “t” from the start of engagement of the clutch 20is represented as a direct function in which the target clutchdifference rotation speed Δ{tilde over (ω)} t gradually decreases as theelapsed time “t” increases and becomes zero after the allowable clutchsynchronizing time Tstmax which corresponds to the target clutchsynchronizing time Tst elapsed. It is noted that when the judgment atthe step S82 is “NO”, the target clutch difference rotation speedΔ{tilde over (ω)} t is the same with the allowable clutch synchronizingtime Tstmax (See bold broken line). Accordingly, the difference rotationspeed Δ{tilde over (ω)} of the clutch 20 gradually drops with time fromthe start of engagement of the clutch 20 along the line of the targetclutch difference rotation speed Δ{tilde over (ω)} t as shown in FIG.10B with the fine line and eventually becomes zero after the targetclutch synchronizing time Tst elapsed and the clutch 20 is synchronized.

Thus, according to the sixth embodiment, before the clutch is engaged,the clutch 20 synchronizing time is controlled to be equal to or lessthan the allowable clutch synchronizing time Tstmax which is calculatednot to exceed the allowable clutch heat generation amount Qtmax.Accordingly, the heat generation amount of the clutch 20 can be surelyprevented from exceeding the allowable clutch heat generation amountQtmax (shaded area in FIG. 10) under the clutch 20 being in engagement.

Other Embodiments

According to the embodiments explained heretofore, at the step S65 inFIG. 4, the control portion 40 controls the rotation speed {tilde over(ω)} MG1 r of the first motor/generator MG1 so that the input shaftrotation speed {tilde over (ω)} i agrees to the target input shaftrotation speed {tilde over (ω)} it_(—)0 at the start of engagement(allowable clutch difference rotation speed Δ{tilde over (ω)} _(—)0maxat the start of engagement). However, the control portion 40 may controlthe rotation speed {tilde over (ω)} MG1 r of the first motor/generatorMG1 so that the input shaft rotation speed {tilde over (ω)} i becomesequal to or less than the target input shaft rotation speed {tilde over(ω)} it_(—)0 at the start of engagement.

According to the embodiments explained heretofore, at the step S70 inFIGS. 4, 11 and 14, the control portion 40 controls the rotation speed{tilde over (ω)} MG1 r of the first motor/generator MG1 so that therotation speed {tilde over (ω)} MG1 r agrees to the target input shaftrotation speed {tilde over (ω)} it during engagement. However, thecontrol portion 40 may control the rotation speed {tilde over (ω)} MG1 rof the first motor/generator MG1 so that the rotation speed {tilde over(ω)} MG1 r becomes equal to or less than target input shaft rotationspeed {tilde over (ω)} it during engagement.

According to the embodiments explained heretofore, at the step S69 inFIGS. 4, 11 and 14, the control portion 40 renews the target input shaftrotation speed {tilde over (ω)} it during the clutch being in engagementand controls the rotation speed {tilde over (ω)} MG1 r of the firstmotor/generator MG1 by feedback control (PID) operation at the step S70in FIGS. 4, 11 and 14 so that he rotation speed {tilde over (ω)} MG1 ragrees to the target rotation speed {tilde over (ω)} MG1 t calculatedabove. However, the control portion 40 may calculate the target clutchdifference rotation speed Δ{tilde over (ω)} t and execute the feedbackcontrol (PID) in a manner explained above, so that the actual clutchdifference rotation speed Δ{tilde over (ω)} r agrees to the targetclutch difference rotation speed Δ{tilde over (ω)} t as calculatedabove.

Further, according to the embodiments explained heretofore, at the stepS61-1 in FIG. 5, the control portion 40 obtains by estimation the clutchtemperature Tcrt which corresponds to the temperature of the frictionmember 22 a based on the housing inside temperature Th detected by thetemperature sensor 26, the heat generation amount of the friction member22 a and the integrated value of the heat dissipation amount of thefriction member 22 a and the clutch 20 as a whole. However, the clutchtemperature Tcrt may be obtained by providing a temperature sensor suchas heat dissipation sensor which detects the temperature of the frictionmember 22 a in the vicinity of the friction member 22 a.

Further, according to the embodiments explained heretofore, the controlportion 40 calculates the input shaft rotation speed {tilde over (ω)} iwhich corresponds to the rotation speed of the input shaft 51 based onthe rotation speed {tilde over (ω)} MG1 r of the first motor/generatorMG1 inputted from the rotation speed sensor MG1-1, the rotation speed{tilde over (ω)} MG2 r of the second motor/generator MG2 (calculatedfrom the vehicle speed V) and the number of teeth between the sun gear11 and the inner gear 14 a. However, an input shaft rotation speeddetecting sensor which detects the rotation speed of the input shaft 51may be provided in the vicinity of the input shaft 51 to directly detectthe input shaft rotation speed {tilde over (ω)} i.

According to the embodiments explained above, at the step S61-3 in FIG.5, the control portion 40 calculates the friction torque Te of theengine EG based on the engine EG oil temperature by estimating the oiltemperature based on the water temperature to detected by the watertemperature sensor EG-3 . However, the control portion 40 may calculatethe engine friction torque Te based on the engine oil temperaturedetected by the oil temperature sensor (not shown) which detects the oiltemperature of the engine EG.

At the step S61-4, the control portion 40 calculates the relationshipbetween the clutch difference rotation speed Δ{tilde over (ω)} _(—)0 atthe start of engagement and the actual clutch heat generation amount Qrwhich relationship is a quadratic function based on the friction torqueTe of the engine EG, engine inertia le and the target clutchsynchronizing time Tst. However, the engine inertia le and the targetclutch synchronizing time Tst are predetermined in advance and thefriction torque Te depends on the engine EG oil temperature. Therefore,the control portion 40 may calculate the relationship between the clutchdifference rotation speed Δ{tilde over (ω)} _(—)0 at the start ofengagement and the actual clutch heat generation amount Qr of the clutch20 by inputting the engine EG oil temperature into the mapping data orthe calculation formula which represents the relationship among theengine EG oil temperature, actual clutch heat generation amount Qr andthe clutch difference rotation speed Δ{tilde over (ω)} _(—)0 at thestart of engagement.

According to the embodiments explained above, at the step S69 in FIG. 4,the control portion 40 renews the target input shaft rotation speed{tilde over (ω)} it during engagement by substituting the target inputshaft rotation speed {tilde over (ω)} it_(—)0 at the start of engagementcalculated at the step S63 or S64, the target clutch synchronizing timeTst, the elapsed time “t” elapsed from the start of engagement of theclutch 20 and the current engine rotation speed {tilde over (ω)} e intothe formula (5) above. However, instead of substituting the currentengine rotation speed {tilde over (ω)} e, the control portion maysubstitute the engine EG rotation speed which is estimated during theclutch 20 engagement into the formula (5) thereby to renew the targetinput shaft rotation speed {tilde over (ω)} it during engagement. Or,the control portion 40 may renew the target input shaft rotation speed{tilde over (ω)} it during clutch 20 engagement by referencing thetarget input shaft rotation speed {tilde over (ω)} it_(—)0 at the startof engagement set at the step S63 or S64, the target clutchsynchronizing time Tst, the elapsed time “t” from the start ofengagement of the clutch 20 and the current engine rotation speed {tildeover (ω)} e to the mapping data which represents the relationship withthe target input shaft rotation speed, target clutch synchronizing time,elapsed time from the start of engagement of the clutch 20, the currentengine rotation speed and the target input shaft rotation speed underthe clutch 20 being in engagement.

According to the embodiments explained above, as shown in FIG. 7, therelationship between the target clutch difference rotation speed Δ{tildeover (ω)} t and the elapsed time “t” from the start of engagement of theclutch 20 is represented as a direct function in which the target clutchdifference rotation speed Δ{tilde over (ω)} t gradually decreases as theelapsed time “t” increases. However, the relationship between the targetclutch difference rotation speed Δ{tilde over (ω)} t and the elapsedtime “t” from the start of engagement of the clutch 20 may berepresented as a quadratic function, or a cubic function in which thetarget clutch difference rotation speed Δ{tilde over (ω)} t graduallydecreases as the elapsed time “t” increases. Still further, therelationship between the target clutch difference rotation speed Δ{tildeover (ω)} t and the elapsed time “t” from the start of engagement of theclutch 20 may be represented as an example such that in the vicinity ofthe above direct function, the target clutch difference rotation speedΔ{tilde over (ω)} t gradually decreases as the elapsed time “t”increases.

According to the embodiments explained above, by gradually engaging theclutch 20, the rotation of the input shaft 51 is transmitted to theoutput shaft EG-1 to start rotation of the engine EG which has beenstopped. However, the clutch 20 is gradually engaged with the clutch 20being in disconnected state and the engine EG in having been startedstate to connect the output shaft EG-1 with the input shaft 51. It isapparent that such embodiment is applicable to the technology accordingto the invention.

Further, according to the embodiments as explained above, a dry, singleplate type clutch is used for the clutch 20. However, the clutch 20 maybe a wet, multiple plate type clutch. It is apparent that suchembodiment is applicable to the technology according to the invention.

Further, as another embodiment, the vehicle with a rotation drive forcefrom the first motor/generator MG1 only under the electric running modeengages the clutch 20 when the vehicle is running with the rotationdrive force from both first and the second motor/generators MG1 and MG2.Such embodiment is also applicable to the technology of the invention.

REFERENCE SIGNS LIST

In the drawings:

-   20: clutch;-   31: first inverter (motor/generator rotation controlling means);-   40; control portion (target clutch difference rotation speed    calculating means, target input shaft rotation speed calculating    means, motor/generator rotation control means, allowable clutch heat    generation amount calculating means, allowable clutch difference    rotation speed calculating means, clutch temperature obtaining    means, target clutch transmitting torque calculating means and    allowable clutch synchronizing time calculating means):-   50: actuator (clutch control means): 51: input shaft 51-   100: hybrid drive device according to the first embodiment-   200: hybrid drive device according to the second embodiment-   EG: engine; EG-1: output shaft-   MG-1: first motor/generator (motor/generator)-   Wl, Wr: drive wheel-   Qtmax: allowable clutch heat generation amount:-   “t”: elapsed time from the start of engagement of the clutch-   Tst: target clutch synchronizing time-   Tstmax: allowable clutch synchronizing time-   Tststd; defined clutch synchronizing time-   {tilde over (ω)} i: input shaft rotation speed-   {tilde over (ω)} it_(—)0: target input shaft rotation speed at the    start of engagement-   {tilde over (ω)} it: target input shaft rotation speed when the    clutch is under engagement-   {tilde over (ω)} e: engine rotation speed-   Δ{tilde over (ω)} r: actual clutch difference rotation speed-   Δ{tilde over (ω)} r_(—)0max: allowable clutch difference rotation    speed at the start of engagement :-   Δ{tilde over (ω)} t: target clutch difference rotation speed-   {tilde over (ω)} MG1 t: target rotation speed of the first    motor/generator-   {tilde over (ω)} MG1 r: rotation speed of the first motor/generator-   Tct: target clutch torque

1. A hybrid drive device comprising: an engine which outputs a rotationdrive force to an output shaft; an input shaft which is rotated inassociation with a rotation of a drive wheel; a clutch disposed betweenthe output shaft and the input shaft for connecting or disconnecting theoutput shaft and the input shaft; a motor/generator which is rotated inassociation with a rotation of the input shaft; an allowable clutch heatgeneration amount calculating means for calculating an allowable clutchheat generation amount which corresponds to a heat generation amountthat the clutch can allow under the clutch being in engagement; and amotor/generator rotation control means for controlling a rotation speedof the motor/generator not to exceed the allowable clutch heatgeneration amount calculated by the allowable clutch heat generationamount calculating means.
 2. The hybrid drive device according to claim1, further comprising: an allowable clutch difference rotation speedcalculating means for calculating an allowable clutch differencerotation speed which corresponds to a difference rotation speed betweenthe output shaft and the input shaft based on the allowable clutch heatgeneration amount, wherein the motor/generator rotation control meanscontrols the rotation speed of the motor/generator so that a clutchdifference rotation speed which corresponds to the difference rotationspeed between the output shaft and the input shaft becomes equal to orless than the allowable clutch difference rotation speed.
 3. The hybriddrive device according to claim 1, further comprising: a clutchtemperature obtaining means for obtaining a current clutch temperature,wherein the allowable clutch heat generation amount calculating meanscalculates the allowable clutch heat generation amount based on thecurrent clutch temperature and a clutch allowable temperature whichcorresponds to a temperature that is an allowable temperature for theclutch.
 4. The hybrid drive device according to claim 2, wherein theallowable clutch difference rotation speed calculating means calculatesthe allowable clutch difference rotation speed at a start of engagementwhich corresponds to the difference rotation speed between the outputshaft and the input shaft at the start of engagement of the clutch andthe motor/generator rotation control means controls the rotation speedof the motor/generator so that the clutch difference rotation speed atthe start of engagement which corresponds to the difference rotationspeed between the output shaft and the input shaft at the start ofengagement of the clutch becomes equal to or less than the allowableclutch difference rotation speed at the start of engagement.
 5. Thehybrid drive device according to claim 2, wherein the allowable clutchdifference rotation speed calculating means calculates the allowableclutch difference rotation speed at the start of engagement whichcorresponds to the difference rotation speed between the output shaftand the input shaft at the start of engagement of the clutch and engagesthe clutch under a current clutch difference rotation speed, when theclutch difference rotation speed before the start of engagement of theclutch is equal to or less than the allowable clutch difference rotationspeed at the start of engagement.
 6. The hybrid drive device accordingto claim 4, wherein the allowable clutch difference rotation speedcalculating means calculates the allowable clutch difference rotationspeed at the start of engagement based on the allowable clutch heatgeneration amount, a friction torque of the engine, an inertia of theengine and a target clutch synchronizing time which is a target elapsedtime from the start of engagement of the clutch to a completion ofsynchronization of the output shaft and the input shaft.
 7. The hybriddrive device according to claim 4, further comprising: a target inputshaft rotation speed calculating means which calculates a target inputshaft rotation speed which corresponds to a target rotation speed of theinput shaft under the clutch being in engagement based on the allowableclutch difference rotation speed at the start of engagement and thetarget clutch synchronizing time which is the target elapsed time fromthe start of engagement of the clutch to the completion ofsynchronization of the output shaft and the input shaft, wherein themotor/generator rotation control means controls the rotation speed ofthe motor/generator so that the rotation speed of the input shaft underthe clutch being in engagement becomes equal to or less than the targetinput shaft rotation speed.
 8. The hybrid drive device according toclaim 7, wherein the target input shaft rotation speed calculating meanscalculates the target input shaft rotation speed so that the targetinput shaft rotation speed becomes zero upon an elapse of the targetclutch synchronizing time from the start of engagement of the clutch bygradually decreasing with time and the motor/generator rotation controlmeans controls the rotation speed of the motor/generator so that therotation speed of the input shaft under the clutch being in engagementbecomes the target input shaft rotation speed.
 9. The hybrid drivedevice according to claim 4, further comprising: a target clutchdifference rotation speed calculating means which calculates a targetclutch difference rotation speed which corresponds to a target clutchdifference rotation speed under the clutch being in engagement based onthe clutch allowable difference rotation speed at the start ofengagement and the target clutch synchronizing time which corresponds tothe target elapsed time from the start of engagement of the clutch tothe completion of synchronization of the output shaft and the inputshaft, wherein the motor/generator rotation control means controls therotation speed of the motor/generator so that the clutch differencerotation speed under the clutch being in engagement becomes equal to orless than the target clutch difference rotation speed.
 10. The hybriddrive device according to claim 9, wherein the target clutch differencerotation speed calculating means calculates the clutch differencerotation speed so that the clutch difference rotation speed becomes zeroupon an elapse of the target clutch synchronizing time from the start ofengagement of the clutch by gradually decreasing with time and themotor/generator rotation control means controls the rotation speed ofthe motor/generator so that the clutch difference rotation speed underthe clutch being in engagement becomes the target clutch differencerotation speed.
 11. The hybrid drive device according to claim 4,wherein the relationship between the allowable clutch differencerotation speed and the elapsed time from the start of engagement of theclutch is a direct function in which the allowable clutch differencerotation speed gradually decreases as the elapsed time increases. 12.The hybrid drive device according to claim 1, further comprising: anallowable clutch synchronizing time calculating means which calculatesan allowable clutch synchronizing time which corresponds to theallowable clutch synchronizing time when the clutch is engaged based onthe allowable clutch heat generation amount and the motor/generatorrotation control means controls the rotation speed of themotor/generator so that the clutch difference rotation speed becomeszero in a time equal to or less than the allowable clutch synchronizingtime by gradually decreasing with time from the start of engagement ofthe clutch.
 13. The hybrid drive device according to claim 1, whereinthe hybrid drive device further includes a target clutch transmittingtorque calculating means for calculating a target clutch transmittingtorque which corresponds to a transmitting torque under the clutch beingin engagement and a clutch control means for controlling the clutch sothat the transmitting torque under the clutch being in engagementbecomes the target clutch transmitting torque.